Matching a formula to a given context

# Matching a formula to a given context

#### Question 1

John is 3 years younger than Mary. Which statement is correct? | ||

a |
Mary's age + John's age = 3. | |

b |
Mary's age = John's age + 3. | |

c |
John's age − Mary's age = 3. | |

d |
John's age = Mary's age + 3. | |

#### Solution (forming an equation)

John's age = Mary's age − 3.

Rearrange the equation.

John's age + 3 = Mary's age.

This shows the statements 'John is 3 years younger than Mary' and 'Mary is 3 years older than John' are equivalent.

Mary's age = John's age + 3. This is option **b**.

Check the answer for a special case. For example:

If John is 10 years old, Mary would be 13 years old.

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