Can someone help me I do not understand any of this

This is so harddd! solve. 1 + 1 = solve 4 + 4 = solve 3 x 3

In the following diagram it is given that dec, ab || dc, ad || eb, and ad is congruent to bc. a)why isn't abc a parallelogram even though it has a pair of parallel sides and a pair of congruent sides b)explain why be must be congruent to bc. further explain what type of triangle this makes triangle abc and what it tells you about angle 1 and angle 2c) finally why must angle 3 be congruent to angle 1? further, explain why we know that angle 3 is congruent to angle 2

Which equation results from adding the equations in this system? x+6y=9 and -x+2y=-15