Since there are 10 slices of cake, you would have to divded the cost ($2,500) by 10 to find out the cost per slice (you would get $250). Since we are finding the cost of 3 slices, you would mulitply 250 by 3, then you get your answer
T= 21.79x + 3.99x + 6.89x where t is the total cost and x is the number of brushes/rollers/paint cans you buy. You don't need a different variable for each item because you buy the same amount of each.
