Ashopper bought a watermelon, a pack of napkins, and some paper plates. in his state, there is no tax on food. the tax rate on non-food items is 5%. the total for the three items he bought was $8.25 before tax, and he paid $0.19 in tax. how much did the watermelon cost? (can you explain how to solve the problem to? )

the answer is $4.45. i started by figuring out the cost of the plates and napkins. the easiest way to figure this cost out is through the tax. we know the way they found the tax is by multiplying the cost of non-food items by the tax rate (5% or 0.5). so, all we have to do to find the cost before tax is set up an equation and work this formula backwards. the equation is 0.19=0.05x where x is the cost of the plates and napkins. now all you do is divide both sides by 0.05 to come up with 3.8=x. now that we know the cost of the plates and napkins is $3.80, all we have to do is subtract this cost from the total cost of $8.25 giving us the cost of the watermelon which is $4.45.