Can someone help me find the right triangle

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 radius of a circle with an area of 78.5 cubic inches? use 3.14 for pie

25 ! i need asap! ! ill mark brainliest!