Please help! How much interest (in dollars) will Alex receive after 2 years if he deposited $14,000 in the bank at 3.5% annual interest rate?

Davit received $870 as an interest for money invested in Foreign Exchange Market three years ago. How much money did he invest, if the annual interest was 4%.

For starting a new business, Arthur borrowed $23000 and calculated $3450 interest for five years. What annual interest was considered?