The interest rate is i.(i is a unknow number). X(X is a unknow number) is the present value of a perpetuity of 1 per year with the first payment at the end of the 2nd year. 20X is the PV of series of increasing payments 1,2,3.... with the first payment at the end of the 3rd year.
Calculate the discount rate, d that is actuarially equivalent to the interest i used in the above two perpetuities.