In your class ⅖ of the students play checkers. Of the students who play checkers ⅚ also play chess. If there are 30 students in the class, how many play checkers and chess? *

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?