The two congruent base angles tell us that this triangle is isosceles, meaning it has two congruent sides. Therefore, we can set the two expressions equal to each other and solve from there.
9x - 73 = 3x + 23
6x - 73 = 23
6x = 96
x = 16
Side = 3(16) + 23 = 48 + 23 = 71
Hope this helps!
