Answer:
m∠B = 111º
Step-by-step explanation:
use law of cosines
c² = a² + b² - 2ab*cosC
---------------------------------
15² = 7² + 11² - 2(7)(11)cosB
225 = 49 + 121 - 154cosB
225 = 170 - 154cosB
Subtract 170 form both sides
55 = -154cosB
Divide both sides by -154
-0.3571428571 = cosB
m∠B = arccos -0.3571428571
use calculator
m∠B = 110.924832425009406
Rounded
m∠B = 111º
