Answer: It will take 8 weeks to Tom to achieve his goal.
Explanation:
Given: The earning of Tom in an hour = $7.5
if Tom worked 15 hours in a week, then the amount earned by him in one week =

The required amount to achieve his goal = $900
The number of week he need to work to achieve his target =

Hence, It will take 8 weeks to Tom to achieve his goal.