Answer
Please see the work below.
Work Step by Step
We know that
$K_c=\frac{[SO_3]}{[SO_2][O_2]^{\frac{1}{2}}}$
We plug in the known values to obtain:
$K_c=\frac{0.0160}{0.0056(0.0021)^{\frac{1}{2}}}$
$K_c=62.3$
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