Answer:
Mary buy $30 / $ 2 = 15 grilled cheese sandwiches
Step-by-step explanation:
five hamburgers cost 42 x 5 = $10
money left for grilled cheese sandwiches = $40 - $ 10 = $ 30
each grilled cheese sandwiches cost $2
Mary buy $30 / $ 2 = 15 grilled cheese sandwiches