I would set all 3 given measures equal to 180.
13x-9+4x+11+2x+7 = 180
19x +9 = 180
19x = 171
x= 9
angle l = 4 (9) + 11= 47
answer = 47
So first you have to find the perfect square that matches up with x^2 + 6x
so half of 6, and square it. your perfect square is 9
x^2 + 6x + 9 = 7 + 9
then, condense the left side of the equation into a squared binomial:
(x + 3)^2 = 16
take the square root of both sides:
x + 3 = ± √16
therefore:
x + 3 = ± 4
x = - 3 ± 4
so your solution set is:
x = 1, -7
