Answer:
x = 9
Step-by-step explanation:
The diagram indicates the smaller triangle is similar to larger triangle since the 2 bottom sides are parallel
Then 12/(12 + 15) = (x + 7)/(x + 7 + 20)
12(x + 27) = 27(x + 7)
12x + 324 = 27x + 189
27x - 12x = 324 - 189
15x = 135
x = 9
