M=4(n-3) make n the subject

The graph below shows the amount of money left in the school’s desk fund, f, after d desks have been purchased. for each new desk that is purchased, by how much does the amount of money left in the school’s desk fund decrease?

What is the solution to the equation 9^(x+1) =27

27 is what percent of 108? 27 is % of 108