AlgebraStructure & Method · Book 1All Chapters

Addition and Subtraction

2-3Rules for Addition

Overview

Same signs: add absolute values, keep the sign. Different signs: subtract smaller from larger absolute value, keep the sign of the larger.

Key ideas

  • Like signs add and keep.
  • Unlike signs subtract; sign of larger |value| wins.
  • Add zero changes nothing.

Worked examples

Example 1

Problem. −8 + (−6)

Solution. Same sign: |−8|+|−6|=14, keep negative → −14.

Example 2

Problem. −7 + 10

Solution. Different signs: 10 − 7 = 3, positive larger → 3.

Practice

Try each one. Click Show answer when ready.

  1. 1.

    −12 + (−5)

  2. 2.

    9 + (−15)

  3. 3.

    −4 + 4

Challenge problems

A little tougher — great for test prep. Click Show answer when ready.

  1. 1.

    Simplify −7 + (−3) + 8 + (−2).

  2. 2.

    Simplify |−5| + (−8) + |−2|.