Hello :) how to do this question?

The final cost of a sale is determined by multiplying the price on the tag by 75%. which best describes the function that represents the situation?

The graph below shows the line of best fit for data collected on the number of cell phones in cell phone cases sold at the local electronic store on four different days

Agroup of five people go out to eat and buy appetizers and main dishes they decide to split the bill so each person pays 20% of the total cost appetizers are $5 and main dishes are $10 write an expression to show how much each person pays explain it with how to solve the problem