DEFG is a trapezoid, DH = GH, EI = FI, and HI = 15.5. Find the value of x.
If you imagine taking a copy of the trapezoid, flip it round 180 degrees and place the sloping edges together, you get a rectangle. Its long edge is DE + GF and that is the same as HI + IH = 2 HI = 31.
So now you have an equation:
All you need to do is solve that equation.