You currently have $2,500 invested at an annual rate of 8%

Investment Amount = $2,500

Future value = $13,500

Annual interest rate( r ) = 8%

Term = "n" years

Future value = Investment Amount × (1+r)^n

$13,500 = $2500 × ( 1+0.08 )^n

(1.08)^n = $13500/$2500

(1.08)^n = 5.4

Applying log on both sides

log [(1.08)^n] = log(5.4)

loga^b = bloga

Therefore, n log [(1.08)] = log (5.4)

n × 0.0334237555 = 0.7323937598

n = 0.7323937598/0.0334237555

n = 21.9123718697 years

It will take 21.9123718697 years or 21.91 years (rounded off) for investment of $2500 to grow to $ 13,500