Question

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

Answer 1

`-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.

`color(blue)(12)+[-4color(red)(+(-9))]" "larr` start with the inner-most brackets.

=`color(blue)(12)+[-4color(red)(-9)]`

=`color(blue)(12)+[color(red)(-13)]`

=`color(blue)(12)color(red)(-13)`

=`-1`

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