Invasive species are
typically spread
through__

try using substitution:

x + y - 6 = x - y. (i'm not giving you the exact answer). since 0 = x - y, then sub 0 in the equation with x - y. combine your like terms, and then use inverse operations, and you'll have your answer.

: -)

answer: 45

explanationyou have to add as well to be it could be

i think that you are smart and you should fit for it out