First you want to see how much she makes per hour so you will divide
$108.75 / 15 = $7.25
Delila she makes $7.25 every hour.
So if next week she works 3 more hours than she did the previous you will just multiply $7.25 three times which is $21.75.
Then just add $108.75 + $21.75 = $130.50.
If Delila works 18 hours she will earn $130.50.
Hope this Helps!!