Hello Amatul,
The problem says Ameesha gets paid $7.50 per hour.
$7.50 per hour means $7.50 for every hour. Another way to look at it is: $7.50 TIMES the number of hours Ameesha works.
That means her pay, P will equal $7.50 times H, the # of hours worked.
P = 7.50H
Cheers.