The rules of exponents tell you to add exponents in the numerator and subtract those in the denominator. A power of a power causes the exponent to be multiplied.
Answer: AC=12 cm
Step-by-step explanation:
To solve this problem you must apply the law of sines, as you can see below:

Where:
a=13
A=85.2°
B=71.6°
Therefore, you must solve for b, then, you obtain that the lenght AC asked in the problem above is:

B) 2 (5 + 7) = 2 × 5 + 2 × 7
Distributing the two multiples the five and seven and adds there them together.
((-9+14)/2, (-20+12)/2)
(5/2,-8/2)
(5/2,-4)