4 cookies cost $7. At this rate, how much will 9 cookies cost?

$15.75

you multiply the 4 cookies by 2 to get 8 ($14), then, you divide 7 by 4 to get the cost of one cookie ($1.75). add that to 14, and thus, your answer.

hello from mrbilldoesmath!

answer:

x - 3

discussion:

x^2 - 9 = (x-3) (x+3)   so

(x^2-9)/ (x + 3) = x-3

you,

mrb