"the advrage a of 2 numbers c and d is equal to half the sum of c and d " this whole qustion confuses the I am basically supposed to put it into a equation but it's just not clicking for me can you help?

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.