A person is six 𝑧 years old. What was their age six years ago?
To find anyone’s age six years ago, we will take their current age and subtract six years. We can do the same thing here. The person is currently six 𝑧 years old — current age six 𝑧. And we need to subtract six years.
The age of a person that is six 𝑧 years old now is equal to six 𝑧 minus six.