Answer: 16 credits
Explanation:
If the cost increases then the credits will increase. The question is asking that if he paid $1218 for 12 credits how many credits will he pay for $1624. Set up a proportional relationship and solve for the number of credits.
1218/ 12 = 1624/x Cross multiply
1218x = 19488
x = 16
This means he took 16 credits