Matrix question just need a tad bit of help

Which equation represents the partial sum of the geometric series?

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

What is the range for 31,39,29,34,37,24,36,33,34,28