Answer: (D) 9
<u>Step-by-step explanation:</u>
This is an isosceles triangle. Since the legs are congruent, then the base angles are congruent.
9x + 3 = 84
<u> - 3 </u> <u> -3 </u>
9x = 81
<u>÷9 </u> <u>÷9 </u>
x = 9
