At the start you will start with $7 and $7.60 there is a simple way and a more complex process. The simple way is using the formula of y=mx+b so y=.8x+7 and the other way is just too add .8 to 7 and .7 to 7.6 and keep doing that till you get the answer. The answer is 7, seven topping have to be added to make them the same price.