Preston has a car washing business. Last year he washed 20 cars a week. This year, he washed 1,200 cars. How many more cars did he wash this year than last year? *52 weeks=1 year

Ineed in figuring out this problem.

Sam opened a money-market account that pays 3% simple interest. he started the account with $7,000 and made no further deposits. when he closed the account, he had earned $420 in interest. how long did he keep his account open?

In the diagram, ab is tangent to c, ab = 4 inches, and ad = 2 inches. find the radius of the circle.