if someone would explain how to do this and give me the final answer that would be nice if you, i just don’t know how to work it out

Find the given elements if matrix d:

Aquadrilateral has exactly 3 congruent sides davis claims that the figure must be a rectangle why is his claim incorrect.

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?