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. using the formula mc006-1.jpg, how many years was his money invested?

Hi there
The formula is
A=p (1+rt)
We need to solve for t
T=[(A/p)-1]÷r
Where
A future value 2200
P present value 1000
R interest rate 0.08
T time?
So
T=((2,200÷1,000)−1)÷0.08
T=15 years

Another time like this question you should post in at mathematics subject
Hope it helps

Answer observational;

How are we suppose to know this