Larry Burbach owed a credit card company $4,000. He paid $350 one month and did not charge any new items. He is charged 1.8% monthly interest on the unpaid balance. How much will his new balance be?

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?