Using the 20/10 rule: you should never borrow more than 20% of your annual net income and monthly payments shouldn't be more than 10% of your monthly net income.
In this situation, we know the yearly net income is $75,000.
First we want to multiply 20% by $75,000 = $15,000
$15,000 is 20% of your yearly net income.
This would be the most you'd want to borrow given the information provided.