Plz help me i really need it

If you are trying to move an attached term across the equal sign (=), what operation would you use to move it?

Diane’s bank is offering 5% interest, compounded monthly. if diane invests $10,500 and wants $20,000 when she withdrawals, how long should she keep her money in for? round to the nearest tenth of a year.

Is experimental probibilty the same as the observed frequency in math? i need the answer asap!