### Substitution into Formulae

This means replacing letters in a formula with numbers. When replacing a letter with a number, use brackets. When there is a number just outside the bracket, it means multiply what is outside the brackets with what is inside the brackets

#### Example 1. What is the value of 2 + 3c when c = 4?

#### Example 2. What is the value of a + 7b when a = 2 and b = 5?

#### Example 3. What is the value of x + yz when x = −5, y = 4 and z = 6?

2 + 3c | = 2 + 3(4) |

= 2 + (3 × 4) | |

= 2 + 12 | |

= 14 |

a + 7b | = (2) + 7(5) |

= 2 + (7 × 5) | |

= 2 + 35 | |

= 37 |

x + yz | = (−5) + (4)(6) |

= −5 + (4 × 6) | |

= −5 + 24 | |

= 19 |

to: