Answer: x = 23
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Step-by-step explanation:
The tickmarks tell us we have two congruent sides. These sides are the same length. The triangle is isosceles.
Opposite the congruent sides are the congruent base angles. In this case, each base angle is 28 degrees.
This triangle has these three angles:
Add up these angles and set the sum equal to 180.
28+28+(5x+9) = 180
5x+65 = 180
5x = 180-65
5x = 115
x = 115/5
x = 23 is the final answer
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Optional Section:
Use the value of x to find the missing angle
5x+9 = 5*23+9 = 115+9 = 124
Then notice adding the three angles gets us: 124+28+28 = 180 which confirms the answer is correct.