Apine tree measured 40 1/2 feet tall. over the next 7 1/2 years, it grew to a height of 57 feet , during the 7 1/2 years what was the average yearly growth rate of the height of the tree?

We know that
40 1/2 feet > (40*2+1)/2> (81)/2 > 40.5 ft
7 1/2 years> (7*2+1)/2> 15/2 > 7.5 years

[the average yearly growth rate of the height of the tree]=(57 ft-40.5 ft)/7.5
[the average yearly growth rate of the height of the tree]=(16.5)/7.5
[the average yearly growth rate of the height of the tree]=2.2 ft/year

the answer is
2.2 ft/year