Find the unit rate of $50 for 6 hours of work

How do you determine if an ordered pair is a solution to a given equation?

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?

What is the value of the discrimination for the quadratic equation 0=×2+2+×2