Question

Please show your work I don't know what to do it's hard

Answer 1

That's basic trigonometry
Tangent 57 degrees = AC / 9
AC = Tangent 57 degrees * 9
AC =  1.5399 * 9
AC = 13.8591 Rounding to one tenth =
13.9

Answer 2

Soh Cah Toa! :)

Sin = Opposite/Hypotenuse
Cos = Adjacent/Hypotenuse
Tan = Opposite/Adjacent 
You are looking for AC, which is opposite. And you are given Adjacent.

tan(57)*9 = length of B which is 13.85 units