I do not agree . 25% of his hourly pay equals $ 2.25 
.25 * 9 = 2.25 
9+2.25=11.25 
He wants his hourly pay to be $12 .
12-9 = $3
so, he needs his hourly pay to be increased by $3 to reach his goal.
$3 is 1/3 of his current hourly pay . 
1/3 = 33% 
now .33*9= $ 3 
* means times ( multiplied by) 
Hope that this helps !