In this case the answer is very simple . .
Step 01:
Data
Initial earnings
1 hour ===> $10
20 hours / week
New earnings
+ 15% hour
$10 * (1.15)
Step 02:
Inicial earnings

New earnings

The difference would be:
New earnings - Inicial earnings = $ (230 - 200) = $30
The answer is:
The difference in money you will earn is $ 30.