To complete the equation \( __ - 3 = -7 \), you need to find the value that, when you subtract 3 from it, equals -7.
To find the value, you can add 3 to both sides of the equation:
\[ __ - 3 + 3 = -7 + 3 \]
This simplifies to:
\[ __ = -4 \]
So, the completed equation is:
\(-4 - 3 = -7\)