Least common multiple of
$10$ and
$20$ is
$20$. Convert
$\frac{33}{10}$ and
$\frac{27}{20}$ to fractions with denominator
$20$.
\frac{66}{20}-\frac{27}{20}
Since
$\frac{66}{20}$ and
$\frac{27}{20}$ have the same denominator, subtract them by subtracting their numerators.
\frac{66-27}{20}
Subtract
$27$ from
$66$ to get
$39$.
\frac{39}{20}