# What is 12+ [ - 4+ ( - 9) ]?

Sep 20, 2016

$- 1$

#### Explanation:

Count the number of terms first. Each term simplifies to a single answer and these are added or subtracted in the last line.

$\textcolor{b l u e}{12} + \left[- 4 \textcolor{red}{+ \left(- 9\right)}\right] \text{ } \leftarrow$ start with the inner-most brackets.

=$\textcolor{b l u e}{12} + \left[- 4 \textcolor{red}{- 9}\right]$

=$\textcolor{b l u e}{12} + \left[\textcolor{red}{- 13}\right]$

=$\textcolor{b l u e}{12} \textcolor{red}{- 13}$

=$- 1$

Terms which are already simplified should be carried down to the next line.