Problem in writing the system of equation in LaTeX

Question

Here's the code I have and here's the system of equation it creates which is not working as desired. Do you know how I can fix it?

\item For what value of $b$ would the following system fo equations have an infinite number of solutions?\hfill
$$\begin{align*} 
3x+5y &=  27 \\ 
12x+20y &=  3b
\end{align*}$$
    \begin{enumerate}
    \item $9$   
    \item $27$ 
    \item $36$
    \item $81$ 
    \item $126$             
    \end{enumerate}

enter image description here

Don't add the outer $$s, then you'll be fine. Also see Why is \[ … \] preferable to $$? for when a display math block is needed. — Werner, May 20 '14 at 20:09

Bernard · Answer 1 · 2018-02-14T14:16:16.647

A suggestion to improve the below solution, using in-line enumerate* environment from the enumitem package, and empheq (that loads amsmath) to have a left brace before the system of equations:

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{fourier}
\usepackage{heuristica}
\usepackage[overload]{empheq}
\usepackage[inline, shortlabels]{enumitem}

\begin{document}

\begin{enumerate}[start = 55]
\item For what value of $b$ would the following system fo equations have an infinite number of solutions?
\begin{align*}[left = \empheqlbrace]
3x+5y &= 27 \\
12x+20y &= 3b
\end{align*}
    \begin{enumerate*}[afterlabel = ~~, itemjoin = {\hspace{1.5em}} ]
    \item $9$
    \item $27$
    \item $36$
    \item $81$
    \item $126$.
    \end{enumerate*}
\end{enumerate}

\end{document}

enter image description here

score 6 · Answer 2 · edited May 21 '14 at 05:19

The package systeme is very handy for typesetting systems of equations. Note how not just the = symbol but also the variables x and y and the symbol + are aligned nicely without requiring any special user inputs (see the comment in my code).

enter image description here

\documentclass{article}
\usepackage{systeme} % see http://www.ctan.org/tex-archive/macros/generic/systeme
\begin{document}
\begin{enumerate}
\item For what value of $b$ would the following system of equations 
   have an infinite number of solutions?
\[
\sysdelim..  % no delimiter symbols on either side
\systeme{
   5y+3x =  27 , % it will be automatically reordered as 3x+5y = 27
   12x+20y =  3b}
\]
    \begin{enumerate}
    \item 9   
    \item 27 
    \item 36
    \item 81 
    \item 126             
    \end{enumerate}
\end{enumerate}
\end{document}

@MoneyOrientedProgrammer - Thanks for the edit. – Mico May 21 '14 at 05:20 — Mico, May 21 '14 at 05:20

score 5 · Answer 3 · edited Jun 10 '20 at 12:32

The align* environment (as well as align) is already a math environment, so you don't need to go into math mode before using align*. In fact, align* can not be used in math mode, but the "inner" math environments such as aligned can be.

enter image description here

References:

You don't need to use \[ in this particular case, but you should have a look at Why is \[ ... \] preferable to $$ ... $$?
An excellent reference for math mode is Herbert Voss' comprehensive review of mathematics in (La)TeX.

Code:

\documentclass{article}
\usepackage{amsmath}
\usepackage{enumitem}
\begin{document}
\begin{enumerate}
    \item[55.] For what value of $b$ would the following system of equations have an infinite number of solutions?
        \begin{align} 
             3x+ 5y &=  27 \ 
            12x+20y &=  3b
        \end{align}
        \begin{enumerate}
            \item $9$

            \item $27$ 
            \item $36$
            \item $81$ 
            \item $126$

        \end{enumerate}
\end{enumerate}
\end{document}

Did you test your code? When I am testing it , it doesn't become the same as yours! — Mona Jalal, May 20 '14 at 21:12
@MonaJalal: Yes I did. The image is the output of the code as posted. Did you try the code exactly as I posted, or did you try it in your real use case? Perhaps you are using different packages, or have some custom settings? There is a reason why it is recommended that you post a fully compilable MWE including \documentclass and the appropriate reproduces the problem. Please provide more details and then perhaps we can figure out the problem. — Peter Grill, May 20 '14 at 21:44

Problem in writing the system of equation in LaTeX

3 Answers3

References:

Code: