\begin{defn}
The set of all integers is denoted by $\mathbb{Z}$, i.e.
$$\mathbb{Z} = \{.., .., -2, -1, 0, 1, 2, ......\} .$$
\end{defn}

\begin{notes}
Note that within this set it is possible to subtract as well as add and multiply. Within this set we cannot, however, in general, perform division.
\end{notes}

When preforming multiple mathematical operations within the same equation, i.e. $79 - 8\cdot 3$, there is a conventional order for which the operations must be performed.

\begin{defn}
The conventional order of operations for equations with multiple mathematical operations is referred to as an \textbf{operator precedence}.
\end {defn}

\begin{xmpl}
To compute $79 - 8\cdot 3$ start by multiplying and then subtracting:\\
$79 - 8\cdot 3 = 79-24 = 55$
\end{xmpl}
\begin{xmpl}
To compute $15 - (24 + 36)$ we first note that the parentheses (brackets) imply a precedence; anything inside brackets should be evaluated first.

Thus, we first add 36 to 24 and then we subtract that from 15.\\
15 - (24+36) = 15 - 60 = - 45\\\

Note that the answer is a negative number.
\end{xmpl}
\begin{xmpl}
Simple arithmetic in R is easily done at the command prompt.
\begin{verbatim}
79-8*3
[1] 55
15-(24+36)
[1] -45
\end{verbatim}
\end{xmpl}