#1**+3 **

We can first use the Law of Sines

sin 60 / 9.2 = sin B ' / 10

10 sin 60 / 9.2 = sin B ' take the arcsin to find B '

arcsin [ 10 sin 60 / 9.2 ] = B ' ≈ 70.27°

But B ' is obtuse so its true measure is 180 - 70.27 ≈ 109.73°

And since the triangle on the left is isosceles and the angle supplemental to 109.73°= 70.27°....then this will also be the measure of B

So

B = 70.27° and B ' = 109.73°

CPhill May 1, 2019