Hi there!
We know that the angles ∠B and ∠A are supplementary because they are both interior angles. Therefore:
180 = ∠A + ∠B
Rewrite:
180 = (6x - 48) + (4x + 38)
Combine like terms:
180 = 10x - 10
Solve for x:
190 = 10x
x = 19
Solve for ∠B by plugging in this value of x:
∠B = 4(19) + 38
∠B = 76 + 38
∠B = 114