Work out m and c for the line y=11x

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

Ijust need to see how to do this. so you don’t have to answer all of them just a step by step explanation of one.

How to use order of operation in 20 divide by 4 multiply 5 = 1