To solve the equation \( x - 78 = -5 \), you can add a number to both sides to isolate \( x \).
We want to find a number to add to both sides. In this case, you can add 78 to both sides:
\[ x - 78 + 78 = -5 + 78 \]
This simplifies to:
\[ x = -5 + 78 \]
Now, calculate the right side:
\[ x = 73 \]
To find out what number we added to both sides, we can see that we added 78.
So, the answer is 78.