a complex answer
皋诚
2026-05-01 05:47:40
( reads)
h1 and h2 are height for both ABF and OEF
SABF=6/7x(1/2)x84x(1/2)=18, the first ½ is for the (h1+h2)=1/2 of BC, the second one is for the half area of the ABCD, quite complex, other solutions are much better.