Broccoli costs $1.50 per pound at a grocery store.how much money does 64 ounces of broccoli cost,before tax.

The conversion factor of ounces to pound is 16 ounces per 1 pound. The ratio and proportion concept is used here. The ratio of the price of broccoli per pound should be the same with that of the price of 64 ounces. 
                     ($1.50 / pound) x (1 pound/ 16 ounces) = (P / 64 ounces)
The value of P in the equation is 6. Thus, the price of 64 ounces of broccoli should be $6. 

Well if -13 is an opposite you could just make in simple which is 13 then -9 is 9 and -19 is 19 and 6 is 0 because it could be going back and forth