Your final balance of an investment of $270 invested at 10% was $459. For what period of time did you invest?

Answer 1

P = Po + Po*r*t.
459 = 270 + 270*0.1*t
t = ?. = Time in years.

Answer 2

Thanks but why did you add 260 twice

Answer 3

In factored form:
P = Po + Po*r*t = Po(1+rt).