Can someone help me answer this question.

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

Can you me find the missing length. i attached an image.

Using elimination, what is -4x+2y=-12 4x+8y=-24