two football players start running towards each other each other from the opposite ends of a 100- yard football field. The faster player runs at a rate of 30 feet per second. The slower player runs 20 feet per second. After how many seconds will they collide

The perimeter of ? cde is 55 cm. a rhombus dmfn is inscribed in this triangle so that vertices m, f, and n lie on the sides cd , ce , and de respectively. find cd and de if cf=8 cm and ef=12 cm. the answer is not cd=20 and de=15. i have tried that one, it does not work.