13. if (x, y) is the solution to the system of equa-
tions shown below, what is the value of x + y?
x + 4y = 20
x + 7y=41
a) – 13
b) -1
c) 1
d) 15

In the diagram of circle o, what is the measure of zabc?

Solve the triangle. a = 21°, c = 105°, c = 5

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.