Susbtitute -1/2x +8 for y in the equation 3x+4y=36 to obtain the value of x.

Substitute the value of x in the equation y=-1/2x+8 to obtain the value of y.

So solution of the equations is (4,6).
Plot the graph of the equation.
The lines intersect each other at (4,6) so solution of equation is (4,6).