Let x = the worth of the investment today (the principal).
Value after 7 years is A = $100
Duration, t = 7 years
Interest rate, r = 5%
Compounding interval, n = 12 (monthly)
Therefore
[tex]A = x(1+ \frac{r}{n} )^{nt}[/tex]
That is,
x(1 + 0.05/12)⁸⁴ = 100
1.418x = 100
x = 70.52
Answer: $70.52
