Gavin needs $80 to buy a fish tank. He has saved $8 and plans to work as a babysitter to earn $9 per hour. Which inequality shows the minimum number of hours, n, that Gavin should work as a babysitter to earn enough to buy the fish tank?

8 + 9n ≥ 80, so n ≥ 8
8 + 9n ≤ 80, so n ≤ 8
9n ≥ 80 + 8, so n ≥ 9.8
9n ≤ 80 + 8, so n ≤ 9.8

Question

Gavin needs $80 to buy a fish tank. He has saved $8 and plans to work as a babysitter to earn $9 per hour. Which inequality shows the minimum number of hours, n, that Gavin should work as a babysitter to earn enough to buy the fish tank?

8 + 9n ≥ 80, so n ≥ 8
 8 + 9n ≤ 80, so n ≤ 8
 9n ≥ 80 + 8, so n ≥ 9.8
 9n ≤ 80 + 8, so n ≤ 9.8

Mercury · Answer

if he earns a wage of $9 per hour, and he works (n) hours, the amount he earns is 9n

add this onto the $8 already saved.

this quantity must be greater than or equal to 80, in order to afford the tank. set up the inequality and solve for n.