Is y=2x-9 proportional or nonproportional

Which of the following is most likely the next step in the series? a3z, b6y, c9x, d12w, е15v, f18u

Ineeeeed this is due tomorrow and i dont know the answer can you find all the exponents

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