Explanation:
EF = 6x - 4
and it is also the combination of EG and GF.
so,
6x - 4 = EG + GF = EG + 13
6x = EG + 17
now, we have additional information. EF bisects CD. that means it cuts CD in half.
and that means both banks must be off equal size.
5x - 1 = 7x -13
12 = 2x
x = 6
so, back to the first problem
6×6 = EG + 17
36 = EG + 17
19 = EG