Whats 99 divided by eight with long divison

Which expression demonstrates the use of the commutative property of addition in the first step of simplifying the expression (-1+i)+(21+5i)+0

Asinusoidal function whose frequency is 1/6pi

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?