Answer
x = 8a - 2
Work Step by Step
To begin the problem, you need to put the values of the trapezoid's sides into an equation, and set it equal to 39a - 7. Make sure to include a variable for the side that you are solving for. I will be using X. It should come out similarly to how it is written on my paper.
Next, simplify the terms so that you end up with (31a - 5) + x = 39a - 7
To finish the problem, you need to subtract (31a - 5) from both sides to get X alone, giving you your final answer of x = 8a - 2
