Joan has a gym gift card worth $100. Each
time she visits the gym, $12 is deducted from
the amount remaining on the gift card. Which
equation can be used to determine the amount of
money (m), in dollars, remaining on the gift card
after Joan visits the gym d times?
A. m = 12 – 100d
B.
m= 12d - 100
C.
m = -12 + 100d
D. m= -120 + 100

None of these answers.

Step-by-step explanation:

You can test all of these by substituting d with 1. If it results in 88, then substitute with 2. If it results in 76, then the answer is good.

A can be ruled out because it will result in a negative number immediately. You cannot go to the gym negative times, so therefore A must be ruled out.

B is incorrect because it will also result in a negative number up until you get to a high enough amount of visits to the gym. If Joan was to visit the gym one time, the card balance would be deducted down to -88 dollars immediately.

On C, the problem is going past 1.

m = -12 + 100d

m = -12 + 100(1)

m = -12 + 100

m = 88

m = -12 + 100(2)

m = -12 + 200

m = 188

D is incorrect because it performs no algebraic equation related to d. Joan could go to the gym 1 or 1000 times and the balance would still be -20.

If I was to guess the equation, it would be m = 100 - 12d