The question asks for the expression that represents "the difference of seven and three times a number."

To solve this, let's break down the phrase:

1. "Three times a number" can be written as $3x$, where $x$ represents the unknown number.
2. "The difference of seven and three times a number" means we subtract $3x$ from 7, which gives us the expression $7 - 3x$.

So the correct answer is the first option: $7 - 3x$.

Would you like further details or have any questions?

Here are 5 related questions you might consider:

1. What is the expression for "the sum of seven and three times a number"?
2. How would you write the expression for "seven less than three times a number"?
3. What is the difference between the expressions $3x - 7$ and $7 - 3x$?
4. How do you represent "three times the difference of a number and seven"?
5. Can you write an equation where the difference of seven and three times a number equals zero?

Tip: When translating word problems into algebraic expressions, focus on key words like "sum," "difference," "product," and "quotient" to determine the correct operation.