Answer:
AB = 55.25
Step-by-step explanation:
Set up an equation where the length of AB is equal to AC minus BC. This will allow us to solve for x, and then the length of AB.
AB = AC - BC
5x + 9 = 87 - (3x + 4)
5x + 9 = 87 - 3x - 4
5x + 9 = 83 - 3x
8x + 9 = 83
8x = 74
x = 9.25
Now plug 9.25 in for x in the equation for AB
AB = 5x + 9
AB = 5(9.25) + 9
AB = 46.25 + 9
AB = 55.25
