Answer: x = 7
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Work Shown:
The third unmarked angle is (9x-25) because the base angles are congruent. Recall the base angles are opposite the congruent sides in an isosceles triangle. The congruent sides are shown with the tickmarks.
Add up the three angles, set the sum equal to 180, and solve for x
(9x-25)+(9x-25)+(104) = 180
18x+54 = 180
18x = 180-54
18x = 126
x = 126/18
x = 7
