Can someone help real quick? I know x=15 but I can't figure out the length.

Answer:
23
Step-by-step explanation:
AB and BC are tangent to circle P, which means that both lines are congruent. Set AB and CB equal to each other:
2x-7=5x-52
3x=45
x=15
Plug 15 into AB:
2(15)-7 = 23
Length of AB is 23.