The annuity pays 17500 a year at an annual interest rate of

Question

Can someone please explain how to do these. (NOT with excel)

1. On your ninth birthday, you received $300 which you invested at 4.5 percent interest, compounded annually. Your investment is now worth $756. How old are you today? 
2. You are scheduled to receive annual payments of $3,600 for each of the next 12 years. The discount rate is 8 percent. What is the difference in the present value if you receive these payments at the beginning of each year rather than at the end of each year? 
3. Trish receives $450 on the first of each month. Josh receives $450 on the last day of each month. Both Trish and Josh will receive payments for next four years. At a discount rate of 9.5 percent, what is the difference in the present value of these two sets of payments? 
4. You are considering an annuity that costs $160,000 today. The annuity pays $17,500 a year at an annual interest rate of 7.5 percent. What is the length of the annuity time period?