Answer:
x = 10
6x - 6 = 54
Explanation:
The hypotenuse of both triangles are 63 and 6x - 6; the second longest sides are 49 (greater than 35) and 42 (greater than 30).
So our proportion:
63/(6x-6) = 49/42
Cross multiply
63*42 = 49*(6x-6)
2646 = 294x-294
2940 = 294x
x = 10
Double-check:
63/(6*10 - 6) = 49/42
63/(60 - 6) = 49/42
63/54 = 49/42
7/6 = 7/6
6x - 6 = 6(10) - 6 = 60 - 6 = 54