Answer:
It takes 1 year.
Step-by-step explanation:
You have to apply simple interest formula, I = (P×R×T)/100 where I represent interest amount, P is principle, R is interest rate and T is number of years :




Yes; his answer is correct.
John can do this by multiple ways, but most likely he just remembered this one. Here are some ways.
1. He used his fingers; he put 1 finger, then another finger, and got 2 fingers up. The answer is 2.
2. He remembered it; usually Kindergarteners learn this and this is very easy to remember.
3. He used the things around him; I have 1 crayon then add another, how many do I have? 2.
Given:
The expression is

To find:
The factors of the given expression.
Solution:
We have,

Splitting the middle term, we get




Therefore, the factors of given expression are (x+3) and (2x-3).