Answer:
41°
Explanation:
Given ∆ABC with exterior angle DCB as 113° and remote interior angle A as 72°, you want the measure of angle B.
Exterior angle theorem
The exterior angle theorem tells you that an exterior angle of a triangle is the sum of the two remote interior angles.
This means we can find the value of one of the remote interior angles by subtracting the other one from the exterior angle.
Step 1: subtract angle A from exterior angle BCD to find angle B.
∠B = 113° -72° = 41°
The measure of angle B is 41°.
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Additional comment
The first step is to be familiar with the angle relations around a triangle. As you can see, making use of the appropriate relation to find the desired angle is a trivial matter.