Answer:
x= the initial price of a meal without discount
he got a $4 coupon, that means he paid for each meal (x-4)
he paid $75 for 5 days with the coupon
we write the equation:
5(x-4)= 75
we solve the equation:
5(x-4)=75
5x-20=75
5x=75+20
5x=95
x=95/5=19
original price for one lunch : $19