I have no clue how to solve. Need help ASAP

What is the common difference in the following arithmetic sequence 7,3,-1,-5

Toyland is having a sale. all items are 20% off. how much will you save on an item that usually sells for 95$ explain your

Ifurniture stores having a weekend sale and is offering 20% discount on patio chairs and table the sales tax on furniture is 6.25 using function composition how can you represent the total amount a that you would need to pay for this furniture that cost x dollars