To rewrite the given expression \( 3(-3y - 3x + 7) \) using addition, you can change each subtraction to addition by factoring out the negative sign. Here's how it looks:
\[ 3(-3y - 3x + 7) = 3(-1)(3y + 3x - 7) \]
Now, we can distribute the \( -1 \) and rewrite the expression:
\[ = 3(0 + (-3y) + (-3x) + 7) \]
Thus, the original expression becomes:
\[ 3( -3y + (-3x) + 7 ) \]
In terms of explicit placeholders, we can say:
\[ = 3( \underline{-3y} + \underline{-3x} + \underline{7} ) \]
So you can fill in the blanks as:
\[ = 3( \underline{-3y} + \underline{-3x} + \underline{7} ) \]