$-10+\left( -21\div2+\left( -1 \right) \right)$
Divide the numbers$-10+\left( -10.5+\left( -1 \right) \right)$
When there is a $+$ in front of an expression in parentheses, the expression remains the same$-10+\left( -10.5-1 \right)$
Calculate the difference$-10+\left( -11.5 \right)$
When there is a $+$ in front of an expression in parentheses, the expression remains the same$-10-11.5$
Calculate the difference$\begin{align*}&-21.5 \\&\begin{array} { l }-\frac{ 43 }{ 2 },& -21 \frac{ 1 }{ 2 }\end{array}\end{align*}$