Mark spent $135 on his comic book collection. He just sold it online for $310. Approximately what is the profit as a percent of his original cost?

When solving this problem: 3025/5.5 = a/90.75 you get 49912.5 which would be the length of one of the sides of a square when the area is only 90.75 inches. is that answer correct, why, and how is it possible?

Ithink i know it but i want to be sure so can you me out ?

What is 74 round to the nearest ten