Find angle b if triangle abc below is isosceles.

The two base angles of an isoceles triangle are equal so we can conclude that

2x - 20 = x + 8

Now we just need to solve for x:

2x - 20 + 20 = x + 8 + 20

2x = x + 28

2x - x = x + 28 - x

x = 28

So, angle B = x + 8 which is 28 + 8 = 36°