Answer
$-7$
Work Step by Step
Use the rule $a-b=a+(-b)$ by replacing $\color{blue}{-6}$ with $\color{red}{+(-6)}$ to obtain:
$-1\color{blue}{-6}=-1\color{red}{+(-6)}$
Since both addends are negative, add their absolute values and copy the negative sign to obtain:
$\begin{align*}
-1+(-6)&=-(1+6)\\\
&=-7\end{align*}$
