Amount=`P(1+r/100)^T`
where p is the principal amount, r is the rate of interest and t is the time period.
first,=>`882=P(1+r/100)^2`..(1)
also,=>`926.10=P(1+r/100)^3`...(2)
dividing (1) by(2)=>we get `r=5`
substituting value of `r=5` in (1) we get `P=800`