Answer:
First, if it's a simple interest problem, convert R percent to r a decimal, r = R/100 = 9%/100 = 0.09 per year, then, solving our equation
I = 4000 × 0.09 × 2
I = 4000 × 0.18
I = $720.00
The simple interest accumulated on a principle of $4,000.00 at a rate of 9% per year for 2 years is $720.00.
Hope this helps. (Compound interest will be added if the equation needs it)