Reduce[x^2 + y^3 == z && x + 2 y == 3 z + 1 && x y z != 0, {x, y, z}]
you get (y == Root[1 - x + 3 x^2 - 2 #1 + 3 #1^3 &, 1] ||
y == Root[1 - x + 3 x^2 - 2 #1 + 3 #1^3 &, 2] ||
y == Root[1 - x + 3 x^2 - 2 #1 + 3 #1^3 &, 3]) &&
z == 1/3 (-1 + x + 2 y) && -x y + x^2 y + 2 x y^2 != 0
How can we get rid of #?
Just like Reduce[6 - 3 x^2 == 2 n^2 + 4 n x, x]
x == 1/3 (-2 n - Sqrt[2] Sqrt[9 - n^2]) ||
x == 1/3 (-2 n + Sqrt[2] Sqrt[9 - n^2])
