9514 1404 393
Answer:
$125 per year
Explanation:
In the 2 years from 2015 to 2017, the spending on lunches increased by ...
$800 -550 = $250
That is an average per year of ...
$250/(2 yr) = $125/yr . . . . average dollar increase per year
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Additional comment
For costs, it is often true that they follow an exponential curve, not a linear one. Ed's spending increased by a factor of 800/550 = 16/11 in the two years, so an average percentage increase of √(16/11) -1 = 20.6% per year.