The product of 8 and 90 is 720 because 0 x 8 is 0 and 9 x 8 is 72 so when you multiply the two together you get 720.
It increased by 7.5% if you subtract the starting value from the new one and then put that answer over the starting value.
from 2007 to 2012 is only 5 years, so we can see this as a compound interest with a rate of 1.2% per annum for 5 years, so

X=40 degree is the correct answer
Algebra
The inverse of -9n is dividing by -9.
