Answer:
8 years approximately
The problem (I'm assuming is):
Solve
.
I put a t in the problem where I suspected it in went.
Step-by-step explanation:

Divide both sides by 100:


Rewrite in logarithm form.

Divide both sides by 0.05:

Put left hand side into calculator:


So about 8 years if I wrote down the equation correctly.
Interest is equal to rs 72
Simple Interest is computed by multiplying the principal to the interest rate and the time.
I = P * r * t
Principal = rs 400
Interest rate = 6%
Term / time = 3 yrs
I = 400 * 6% * 3
I = 72 the total interest that must be paid in 3 yrs.
You don't need to start with the greater number. Either order of numbers will work because addition had a communitive property, meaning it can be added in any order to get the same answer.