One pound of coffee cost $3.75, then 5 pounds cost 5 x $3.75 = $18.75
Applying the discount of the coupon, the final cost is $18.75 - $1.75 = $17
Without the discount, the cost of p pounds is 3.75p
With the discount, the cost of p pounds is 3.75p - 1.75
Cost of 5 pounds: $17
Cost of p pounds: 3.75p - 1.75