Could you help me out with this question? (Sin, Cos, Tan.) (Soh, Cah, Toa.)

How can you construct perpendicular lines and prove theorems about perpendicular lines

See attachment below and find the equivalent of tan(∠qsr)

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?