So in this case f(x) is number of pollinated flowers and x is the days. First you will need to determine the number of flowers pollinated at days 4 and 10 and the days in between. f(4)= 3(4^2)= 3*16 = 48 f(5)= 3(5^2)= 3*25 =75 f(6)= 3(6^2)=3*36=108 f(7)= 3(7^2)=3*49=147 f(8)= 3(8^2)=3*64=192 f(9)= 3(9^2)= 3*81=243 f(10)= 3(10^2)=3*100=300 Now we need to find the average increase, so that will be the average of the differences between days [(75-48)+(108-75)+(147-108)+(192-147)+(243-192)+(300-243)]/6 =(27+33+39+45+51+57)/6=42