Aforest fire covers twice the amount of forest as it did 3 days ago. if the fire covered 300 square miles 3 days ago and it continues to grow at the same rate, how many square miles will it cover 12 days from now?

This would depend on if we assume this is constant or exponential growth.  If it is linear then it would be:

600=3m+300

300=3m

100=m

A=100d+300

A(12)=1500 mi^2

If it is exponential:

600=300r^3

2=r^3

r=2^(1/3)

A=300(2)^(d/3)

A(12)=4800 mi^2