There are 15 years was his money invested.
<h3>What is simple interset?</h3>Simple Interest is an easy method of calculating the interest for a loan/principal amount.
Given
Frank invests $1,000 in simple interest investment account that pays 8% a year.
After a number of years, he withdraws his balance of $2,200.
The number of years was his money inversted is;
Where p is the principal amount, r is the rate of interest, I is the amount and t is the time.
Substitute all the values in the formula;
Hence, in the 15 years was his money invested.
To know more about investing click the link given below.