Two linear equations in x and y can be interpreted as two straight lines. The algebraic solution is the intersection point of these two lines.
g : 3x + 4y = 12
h : y = 2x - 8
S = Intersect[g, h]
You can both change the equation (right click, edit) and move or rotate the line with the mouse (Move, 3.2.1; Rotate, 3.2.1)