20 12-20 13 the idea of solving the last question of math test 25 at the end of last semester in Fengtai Grade Three.
In the third case, it is easy to get a parallel CE, let OE be X, EB be 5-x, the triangle FEO is similar to Deb, and X/5-X = of/BD = cf/2ce, so 2x/5-x=OF/CE. Triangle AOF is similar to AEC, of/CE = 5/5+X, so 2x/. Then it can be solved. This is what our teacher said. I hope to adopt.