**Answer:**

The amount of time is 8 years

**Step-by-step explanation:**

Simple interest refers to the interest produced by initial capital over a period of time. This does not accumulate to the capital to produce the interests of the following period, so the interest generated or paid in all periods is the same, while the interest rate and term dont vary.

The amount of interest paid or charged depends on three important amounts: Capital, rate and time. This is expressed by the following equation:

<em>**I = P * r * t
**</em>

Where:

- I = interest
.
- P = initial capital
.
- r = interest rate in decimals (it is usually a given data in percentage, which you must divide by 100 to get the value in decimals)
.
- t = time in years
.

In this case I has a value of $ 720, P has a value of $ 1000 and r of 9%, which making the conversion to decimal is 0.09

Replacing in the equation you get:

**<em>720=1000*0.09*t</em>**

Multiplying 1000 * 0.09 you get:

720=90*t

Dividing both sides by 90, in order to isolate t, you get:

<u><em>**8=t**</em></u>

Remembering that the value of t is expressed in years, this means that <u><em>**the amount of time is 8 years**</em></u>.