Example 3. The mathematical expectations of two random variables $X$ and $Y$ are known: $M(X)=3, M(Y)=2$.

Find the mathematical expectations of the sum and difference of these variables.
Solution. Based on formulas (2.4.12) and (2.4.14), we conclude that

$$
\begin{aligned}
& M(X+Y)=M(X)+M(Y)=3+2=5 \\
& M(X-Y)=M(X)-M(Y)=3-2=1
\end{aligned}
$$