Use substitution to solve 3x-2y=11 and x+2y=9

Solve the second equation for 2y.

... 2y = 9 - x

Substitute that into the first equation.

... 3x - (9 - x) = 11

... 4x - 9 = 11

... 4x = 20

... x = 5

Using our expression for 2y above,

... 2y = 9 - 5

... y = 4/2 = 2

The solution is (x, y) = (5, 2).