If a price goes down $4.25 than it is a negative integer. Same situation if a price goes down $2.75; it is still a negative integer. These two numbers can be expressed as -$4.25 and -$2.75. Finding the overall change causes for adding. Same signs add and keep different signs subtract. -4.25+-2.75=7.00. Therefore, the overall change in price for the two days is -$7.00.
