Final answer:
The mathematical expression for 'Seven times the difference of a number and 7' is 7(n - 7), option d.
Step-by-step explanation:
To translate the phrase 'Seven times the difference of a number and 7' into a mathematical expression, we need to break it down. The difference of a number and 7 can be represented as (n - 7), where 'n' is the number. To find seven times this difference, we multiply it by 7, giving us 7(n - 7). Therefore, the correct expression is 7(n - 7), which is option d.