Since the figures are similar, the ratio of corresponding sides is constant.
AB corresponds to EH, the ratio of their side lengths = 14 / (9 1/3) = 1.5 or 3/2
BC corresponds to HG, the ratio of their side lengths = 15/10 = 1.5 or 3/2
CD corresponds to GF, the ratio of their side lengths = 18/12 = 1.5 or 3/2
AD corresponds to EF, so the ratio of their sides must be 3/2
The length of AD is 12.
so
AD/EF = 12/EF = 3/2
Solving for EF: 3/2 * EF = 12 ---> EF = 12 * 2/3 - 8
