PV of a bond when the market discount rate is not known?

I need to be able to find r using excel preferably or a financial calculator

Equation 1 is a general formula for calculating a bond price given the market discount rate: (1) where PV = present value, or the price of the bond PMT = coupon payment per period FV = future value paid at maturity, or the par value of the bond r = market discount rate, or required rate of return per period N = number of evenly spaced periods to maturity

PMT PMT PV = (1+r)? . (1+r)? + + + PMT + FV (1+r)^ PMT PMT PV = (1+r)? . (1+r)? + + + PMT + FV (1+r)^