To solve an equation for an unknown value,

keep the equation

balanced while

isolating the unknown.

To isolate an unknown value, use opposite operations.

Remember, addition and subtraction are opposite operations, and multiplication and division are opposite operations.

To isolate *x*, use opposite operations.

4.2 is added to *x*. So, to get *x* by itself, subtract 4.2.

To keep the equation balanced, subtract 4.2 from both sides of the equation.

*x* + 4.2 | = | 5 |

*x* + 4.2 − 4.2 | = | 5 − 4.2 |

*x* | = | 5 − 4.2 |

*x* | = | 0.8 |

To isolate *x*, use opposite operations.

*x* is multiplied by 4. So, to get *x* by itself, divide by 4.

To keep the equation balanced, divide both sides of the equation by 4.

4*x* | = | 20 |

4*x* ÷ 4 | = | 20 ÷ 4 |

*x* | = | 20 ÷ 4 |

*x* | = | 5 |