Let each instalment be Y₹,
Value of 1100 at the end of the 1st year = 1100x(1 + (20/100)) = 1100 x 1.2 = 1320₹.
As Y₹ is paid at the end of 1st year, the remaining amount i.e. ₹(1320 - Y) has to be paid at the end of 2nd year.
=> (1320 - Y)(1 + 0.2) = Y.
=> Y = 720₹.