Answer:
so amount is 8d / 3 or 2.667 d
Explanation:
given data
invest amount = $d
rate r = k%
interest = $600
time t = 2 year
to find out
amount invested with interest #2400 for 3 year
solution
we will apply here interest formula that is
interest = principal × rate × time  / 100    ........................1
put here value we get 2 equation
600 = ( d × k × 2 )  / 100   ..............a
dk = 30000 Â Â Â Â Â ...................2
and for 2400 interest for 3 year
2400 =  ( amount × k × 3 )  / 100  ................b
amount × k = 80000     .....................3
so from equation 2 and 3 Â
amount × (3000/d) = 80000
amount = 8d / 3
so amount is 8d / 3