Answer
$-\frac{1}{12}$
Work Step by Step
The $LCD$ of $4$ and $3$ is $12$. Changing the given fractions to equivalent fractions that use the $LCD$, then the given expression is equivalent to
$$\begin{aligned}
&
\frac{1}{4}\cdot\frac{3}{3}-\frac{1}{3}\cdot\frac{4}{4}
\\&=
\frac{3}{12}-\frac{4}{12}
.\end{aligned}
$$
Adding/Subtracting similar fractions involves adding/subtracting the numerators and copying the common denominator. Therefore,
$$
\frac{3}{12}-\frac{4}{12}=\frac{3-4}{12}=\frac{-1}{12}=-\frac{1}{12}
.$$
