Hello!
To find ∠B, we will want to find ∠C. As all of the interior angles of a triangle add up to 180°, we could subtract the measures of angles A and C to find B.
First of all, our 113° angle and ∠C are supplementary. This means that their angle measures add up to 180°. As you can see, combining their angle measures would make a semi-circle, or a straight angle.
113+c=180
We subtract 113 from both sides.
c=67
Therefore, angle c is 67°.
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Now, we need to find ∠B. We know that all of the interior angles equal 180°. This gives us the equation below.
72+67+B=180
139+B=180
B=41
Therefore,
°
I hope this helps!