Gannon has deposited $742 in a savings account that earns interest at a rate of 3.4% compounded monthly. What will the account balance be in 15 years?

Firstly, solve the effective annual interest (ieff) with the equation,

ieff = (1 + i/m) ^m - 1

where i is the interest rate and m is the number of times the interest is compounded in a year. In this problem, m is 12

Substituting the values,

ieff = (1 + 0.034/12) ^12 - 1 = 0.03453

To solve for the future (F) amount of the present investment (P),

F = P x (1 + ieff) ^n

where n is number of years.

F = ($742) x (1 + 0.03453) ^15

Thus, the answer is $1234.76.