A = P (1 + r)^t, where A is the final amount, P is the initial amount, r is the annual interest rate as a decimal fraction, and t is the number of years (number of compounding periods).
Substituting the givens: $35000 = P(1+0.036)^3
$35000 Solving for P: P = ----------------- = $31476.67 (answer) (1.036)^3