Factor Completely
x^4 - 2x^3 - 15x^2

It comes out of vehicles which pollutes the air

The question is kind of confusing. if it's asking how many variations of answers can you give. then do 4^5 for your answer.this would be something like the first question could be a and the 2nd c or first b next c etc. if you can, ask the teacher for a better confirmation of what it's asking. if i'm assuming correctly what it's asking, it's 625 different variations.

4x 20 is 80 but if ther machine is broken then there is none you have to redo the test