Respuesta :

start off by knowing that the two triangle are congruent. By knowing this you can turn the given numbers into fractions.

9/72 = 7/7x+7

then cross multiply, which equals

63x + 63 = 504

then solve this equation

63x = 441 - subtract 63 from both sides
x = 7 - divide by 63 from both sides

so your answer is x=7