Question 22367
The interest formula you need is Interest = (Principal)*(rate)*(time)

For Kishan you have Principal is 3000, rate is "x", time is 3yrs.
So Kishan interest is 9000x

For Uma you have Principal is 1800, rate is "(x+0.02)", time is 3yrs.
So Uma interest is 5400(x+0.02) = 5400x + 108

Equation:
   Kishan int. + Uma int. = 1836
       9000x  +  5400x +108 = 1836
                 14400x  = 1836
                      x  = 0.12
So, the two interest rates are 12% and 14%

Cheers,
Stan H.