Problem 1)
Answer: x = 9
x is a midsegment of the triangle so it is half of the parallel side (18)
half of 18 is 9
18/2 = 9
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Problem 2)
Answer: x = 5
In reverse of problem 1, we double the value 2.5 to get 5
The segment 2.5 units long is half that of the side x
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Problem 3)
Answer: x = 11
Similar to problem 1, we divide 22 in half to get 11
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Problem 4)
Answer: y = 35
The two triangles are similar. Therefore, they have congruent corresponding angles. The 35 degree angle and the y degree angle are corresponding angles that are congruent (due to the parallel horizontal lines)
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Problem 5)
Answer: y = 90
This is similar to problem 4. The 90 degree angle (marked by the square box symbol) and the y degree angle are congruent. They are corresponding angles. We have two similar triangles.
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Problem 6)
Answer: y = 50
As you can probably guess by now, problem 6 is similar to problems 4 and 5. The 50 degree angle and the y degree angle are congruent corresponding angles. So that's why y = 50.