93.75h. Mr. Demir must work 93.75h at his part-time job to make sure that he and his wife have met their monthly budget.
This problem can be solved by simply arithmetic, The montly budget is $5,500, Mrs. Demir takes home $4,000 each month. Then what remains to achieve the budget is:
$5,500 - $4,000 = $1,500
Mr. Demir works part time and earns $16 per hour, In order to achieve the monthly budget, Mr. Demir need to take home $1,500. Then, to take home $1,500 Mr. Demir has to work:
1500/16 = 93.75
Mr. Demir has to work 93.75 hours per month in order to achieve the monthly budget