Thirty-nine and seventy-two hundredths in decimal point

Iam at home. /: i am playing video games. translate the following statement into symbolic form.

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?

Abc manufacturing has a policy that it will reject a shipment of parts from its supplier if inspectors find any defective parts in a random sample of 6 parts from the shipment. the supplier has been in business many years and has a long-term defective rate for parts of 6.2% what is the probability that a shipment will be rejected after a given sample of parts is checked?