lisa has 42$ in her luch acount. she spends $2.75 on lunch. witch exspreshion represents this situation

Question

i need help for a math test on my study guied 

Answer 1

y = 42 - 2.75x where x = number of lunches she had, y = how much money she has left

42/2.75 = 8.4/.55 = at most 15 lunches that she can afford