Y- intercept of 6x-3y=24

What is the smallest integer n such that n\sqrt{2} is greater than 20

How to do this , and can some one explain

At the beginning of year 1, carlos invests $600 at an annual compound interest rate of 4%. he makes no deposits to or withdrawals from the account. which explicit formula can be used to find the account's balance at the beginning of year 5? what is, the balance?