What is the hydronium ion (h3o+) concentration in milk if it has a ph of 8.2?

With #! i’ve tried to figure it out but i can’t.

Combine like terms to make a simpler expression 3z+z

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?