x = 10.1
step-by-step explanation:
all of the angles of a tirangle add up to 180º
180 - 65 = 115 (since we already know the value of one angle)
(2x + 7) + (8x + 7) = 115
(combins like terms) 10x + 14 = 115
(isolate the variable subtract 14 from both sides): 10x = 101
(find the variable divide both sides by 10): x = 101/10
x = 10.1