School A sent some students to a revision day. School B sent twice as many students as School A. School C sent 3 fewer students than School A. Each student paid £10 for the revision day. The students paid a total of £2170 Work out how many students were sent by each school to the revision day. You must show all your working.

Given: ae ≅ ce ; de ≅ be prove: abcd is a parallelogram. we have that ab || dc. by a similar argument used to prove that △aeb ≅ △ced, we can show that △ ≅ △ceb by. so, ∠cad ≅ ∠ by cpctc. therefore, ad || bc by the converse of the theorem. since both pair of opposite sides are parallel, quadrilateral abcd is a parallelogram.