The total cost of buying "n" hamburgers can be represented by the expression 2.75n How much would purchasing 10 hamburgers (n=10) cost?

Joe has a rectangular chicken coop. the length of the coop is 4 feet less than twice the width. the area of the chicken coop is 510 square feet. what is the length of the chicken coup?

I’m still confused on how to work the percentages

Ineed to know the ordered pairs for this equation i need the answer quick because it’s a timed test