Which of these is most responsible for global deforestation? A. forest fires
B. climate change
C. increased need for furniture
D. increased demand for agriculture

I would suggest the answer D, but there are multiple reasons for deforestation

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.

: -)