A person invested  2/3rd of his capital at 3%,  1/6th  at 6% and the remainder at 12%. If his annual income is Tk. 25, then the capital is

If capital is x,

Income from 2/3rd is = (2x*0.03/3)

Income from 1/6th is = (x*0.06/6)

Income from rest or (1- 2/3 - 1/6) or, 1/6th is = (x*0.12/6)

Now,

(2x*0.03/3) + (x*0.06/6) + (x*0.12/6) = 25

or, 6x/300 + 6x/600 + 12x/600 = 25

or, (12x+6x+12x) / 600 = 25

or, 30x = 25*600

or, x = 25*600/30

or, x = 500