If b = the rate a boat travels and c = the rate of the current, then which of the following expressions represents the rate of the boat traveling against the current? b + c
b - c
bc
b/c

Last month, a 770 g box of cereal was sold at a grocery store for $3.10. however, this month, the cereal manufacturer launched the same cereal in a 640 g box, which is being sold at $2.50. what is the percent change in the unit price?