You are given that "The number of small dogs shampooed per day was 12 when the price given originally ($20) was in effect". If d= ax+ b (d being number of dogs shampooed at x dollars per dog) that says 12= a(20)+ b. You are also told that "The number of small dogs shampooed per day decreases by 2 for every $5 increase in price". So if the price increases to 20+ 5= $25, the number of dogs shampooed will decrease to 12- 2= 10 dogs. That means that 10= a(25)+ b. Solve the two equations 20a+ b= 12 and 25a+ b= 10. (You can immediately eliminate b by subtracting the first equation from the second.)