9514 1404 393
Answer:
x = 12
Step-by-step explanation:
We can find x using either the measure of angle B, or the measure of angle A.
Using A, we have ...
48 = x^2 -8x
Adding 16 completes the square:
64 = x^2 -8x +16 = (x -4)^2
Then the positive solution is ...
√64 = x -4
x = 4 +8 = 12
The triangles are similar when x=12.
__
Check
We expect angle B to be 84° when x=12:
(x^2 -5x) = x(x -5) = 12(7) = 84 . . . . as needed
