Answer :
The meal is going to be 325 calories plus 12 calories times the number of chips. Set that equal to 541 calories and then use algebra to find the number of chips.
541 = 325 + 12c
216 = 12c
18 = c
541 = 325 + 12c
216 = 12c
18 = c
18 chips, first you subtract 541 by 325, then you divide 216 by 12, you get 18. To check this you do 18x12+325=541 :)