Interest amount earned =$568.75
Principal amount invested = $2500
Rate of interest per year = 6.5%
Let us assume the time taken to gain the interest amount = x
Then
Interest = Principal * Rate * Time
568.75 = 2500 * (6.5%) * x
568.75 = 2500 * (6.5/100) * x
568.75 = 25 * 6.5 * x
568.75 = 162.50x
x = 568.75/162.50
= 3.5 years
So it will take 3.5 years to earn the interest amount mentioned in the question. I hope the procedure is simple enough for you to undertsand.