In triangle abc m∠a 25 m∠b =55 and c=25 find b round your answer to the nearest tenth
a.10.7
b.12.9
c.48.5
d.20.8

Given are the following:
m∠A = 25
m∠B = 55
c = 25

First, get the value of m∠C by getting the third angle of a triangle. We all know that it should sum up to 180. So we have,
180 - 25 - 55 = m∠C = 100   

After getting the value of m∠C and its opposite side is given, we can use the law of sine to find of b

c / m∠C = b / m∠B
25 / sin 100 = b / sin 55      ⇒ substituting the given values to the equation
25(sin 55) / sin 100 = b       ⇒ simplify
20.79 = b

b = 20.8   ⇒ answer (D)