∠A and ∠B\angle B ∠B are supplementary angles. If m ∠A=(x−18)∘\angle A=(x-18)^{\circ} ∠A=(x−18) ∘ and m ∠B=(x−20)∘\angle B=(x-20)^{\circ} ∠B=(x−20) ∘ , then find the measure of ∠B\angle B ∠B.

Given:

∠A and ∠B are supplementary angles.

m∠A=(x−18)° and m∠B=(x−20)°.

To find:

The measure of ∠B.

Solution:

Sum of supplementary angles is always 180 degrees.

∠A and ∠B are supplementary angles. So,

Now,

The measure of angle B is

Therefore, the measure of ∠B is 89°.

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