Concept:
For a moderately skewed distribution, the empirical relationship among mean, median and mode is
\[
\text{Mode}
=
3(\text{Median})
-
2(\text{Mean}).
\]
This relation is one of the most frequently used results in statistics.
For a normal distribution specifically,
\[
\text{Mean}=\text{Median}=\text{Mode},
\]
and the empirical relation is also satisfied.
Step 1: Write the empirical relation.
\[
\text{Mode}
=
3(\text{Median})
-
2(\text{Mean}).
\]
Using the notation of the question,
\[
\mu_3
=
3\mu_2
-
2\mu_1.
\]
Step 2: Rearrange the expression.
Transposing terms,
\[
2\mu_1
=
3\mu_2-\mu_3.
\]
Therefore,
\[
\mu_1
=
\frac{3\mu_2-\mu_3}{2}.
\]
For a normal distribution,
\[
\mu_1=\mu_2=\mu_3.
\]
Hence,
\[
3\mu_2-2\mu_3
=
\mu_1.
\]
Step 3: Substitute the required expression.
The quantity asked is
\[
3(\text{Median})-2(\text{Mode})
=
3\mu_2-2\mu_3.
\]
Using the relation above,
\[
3\mu_2-2\mu_3
=
\mu_1.
\]
Therefore,
\[
\boxed{\mu_1}
\]