O1 The relationship between the number of $4 lunches you buy with a $100 school lunch card and the money remaining on the card

Every time you buy a $4 lunch, $4 is subtracted from the remaining balance on your school lunch card. If x represents the # of lunches you've bought, then

the $ remaining on the card = $100 - ($4) x. If x=0 (no lunches), you have $100 on the card; if x = 25, you have 0 remaining.