For an art project, Corinne and Amelia want to combine their colored pens and distribute them equally among 12 first graders. If Corinne has 84 colored pens and Amelia has 72 colored pens, how many pens does each first grader get?

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.