Problem 2
We have an isosceles triangle because of the two congruent sides (21 each).
The angles opposite the congruent sides are known as the base angles, and the base angles are congruent. For now, we don't know what they are. They are both x. I recommend writing 'x' onto the diagram where that missing unmarked angle is.
Then we'll use the idea that all three angles of any triangle always add to 180
x+x+38 = 180
2x+38 = 180
2x = 180-38
2x = 142
x = 142/2
x = 71
Answer: Choice A) 71
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Problem 3
We use the same ideas as the previous problem. This time the base angles are 56 degrees each. The remaining angle is x.
x+56+56 = 180
x+112 = 180
x = 180-112
x = 68
Answer: Choice A) 68