Ineed with my college math modelling class, here's the "question"
(it's not middle school its college)
there are many formulas for estimating the annual cost of driving. the automobile club estimated that fixed costs for a small car -- including insurance, registration, depreciation, and financing -- total about $5000 per year. the operating costs for gasoline, oil, maintenance, tires, and so forth were about 12.5 cents per mile. (source: automobile association of america)

write an equation for the annual driving cost, c, in terms of d, the number of miles

all appreciated