Let the sum be P

Amount After 2 years = P$\left(1 + \dfrac{R}{100}\right)^T$ = P$\left(1 + \dfrac{5}{100}\right)^2$=P$ \left(\dfrac{105}{100}\right)^2$=P$\left(\dfrac{21}{20}\right)^2$

Given that amount After 2 years = 882

=> P$\left(\dfrac{21}{20}\right)^2$ = 882

=> P = $\dfrac{882 \times 20 \times 20}{21 \times 21} = 2\times 20 \times 20 = Rs.800$