So we know that all triangles equal 180 degrees, basically the equation will look like this 
(7x-11) + (2x-3) + (5x-2) = 180
So first we need to collect like terms
7x + 2x + 5x -11 - 3 - 2 = 180
= 14x -16 = 180
Then we need to move the constant to the right
14x = 180 + 16
Then add 
14x = 196 
Then divide both sides 
The answer is 14 :)