Tim wants air conditioning in his room. The air conditioner costs $40, and each day the electricity costs $1.

Write an expression that can be used to find the cost to run the air conditioner for $ d $ days. If Tim spent a total of $85 on cooling his room, how many days did he use the air conditioner?

A) Expression: Cost = $40 + $1d; Days = 45
B) Expression: Cost = $1d - $40; Days = 125
C) Expression: Cost = $40d + $1; Days = 85
D) Expression: Cost = $40 + $1d; Days = 90

The expression to find the cost to run the air conditioner for d days is Cost = $40 + $1d. If Tim spent $85 on cooling his room, he used the air conditioner for 45 days.

Explanation:

To write an expression that can be used to find the cost to run the air conditioner for d days, we can use the expression: Cost = $40 + $1d. This expression includes the initial cost of the air conditioner, which is $40, plus the cost of electricity for each day, which is $1 times the number of days(d).

If Tim spent a total of $85 on cooling his room, we can set up an equation using the expression: $85 = $40 + $1d. Then we can solve for d by subtracting $40 from both sides and dividing by $1. The value of d is 45 days.