The given statement is:

"Add 3 to a number to get 12."

Let the unknown number be $x$. According to the statement, adding 3 to this number gives 12, which can be written as:

$x + 3 = 12$

This matches option B from the provided choices.

So, the correct answer is: B

Would you like a more detailed explanation or further help?

Here are five related questions to expand on this:

1. How would you solve the equation $x + 3 = 12$ to find $x$?
2. What would the equation look like if the statement said "Subtract 3 from a number to get 12"?
3. Can you write an equation for the statement "Multiply a number by 3 to get 12"?
4. What happens if we divide a number by 3 to get 12? How would the equation change?
5. What is the difference between linear equations like $x + 3 = 12$ and other types of equations like quadratics?

Tip: When translating word problems into equations, focus on keywords like "add," "subtract," "multiply," and "divide" to identify the corresponding mathematical operations.