Answer:
About 31 days
Step-by-step explanation:
Since he already has $125, you can subtract that amount from how much he needs to earn. $400 - $125 = $275 that he must earn.
Divide the remaining amount by how much he earns a day to find the number of days he must work to reach his goal.
$275 ÷ $9 ≈ 30.5 (I got 30.5 repeating). I rounded up to 31 days.