solve without excel

It is known that an investment of $400 will increase to $3200 at the end of 20 years. Find the sum of present values of three payments of $20,000 each which will occur at the end of 20, 40, and 60 years. Q2. (a) (6 marks) (b) Simon wishes to accumulate $50,000 in an investment fund at the end of 20 years. If he deposits $1000 in the fund at the end of each of the first 10 years and $1000+X in the fund at the end of each of the second 10 years, find X if (6 marks) the fund earns 7% effective interest rate