Two triangles: left triangle with y degrees and 40 degrees and right triangle with x degrees.
- 40 degrees from the left triangle, when adding with the unknown angle of the right triangle, is equal to 180 degrees.
- Adding left triangle's (third) undetermined angle and x degrees angle (the other same angle), is equal to 90 degrees.
- The right triangle is an isosceles triangle, meaning two equal angles, and one of them is x degrees. Thus, the other same angle is also x degrees.
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1) Subtract 180 - 40 = 140 degrees. 140 degrees is the unknown angle of right triangle.
2) 140 + x + x = 180 (equation)
- 140 + 2x = 180
- 2x = 180 - 140
- 2x = 40
- x degrees = 20 degrees
ANSWER: x = 20 DEGREES
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1) With knowledge of x degrees being 20 degrees, the other same angle is 20 degrees, too.
2) Subtract 90 - 20 = 70 degrees. 70 degrees is the (third) undetermined angle
of left triangle.
2) 70 + 40 + y = 180
- 110 + y = 180
- y = 180 - 110
- y = 70 degrees
ANSWER: y = 70 DEGREES
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Whew. Hope this helps you out, and let me know asap if you're confused on any part.