Final answer:
The expression 'four less than the product of a number and three' can be represented as 3x - 4.
Step-by-step explanation:
The expression four less than the product of a number and three can be represented as 3x - 4.
Let's break it down. The product of a number and three is 3x, and when we subtract four from it, we get 3x - 4.
Therefore, the correct answer is b. 3x - 4.