3. Insert arithmetic operation signs and parentheses into the expression consisting of three numbers, $\frac{1}{8} \ldots \frac{1}{9} \ldots \frac{1}{28}$, so that the result of the calculations is equal to $\frac{1}{2016}$.

ANSWER: $\frac{1}{8} \times \frac{1}{9} \times \frac{1}{28}$ or $\left(\frac{1}{8}-\frac{1}{9}\right) \times \frac{1}{28}$
Solution: factorize 2016 into prime factors and notice that 2016=8x9x28.