To solve the equation \( x - 3.41 = -19 \) for \( x \), you should isolate \( x \) by adding the same value to both sides of the equation. In this case, you want to eliminate the \( -3.41 \) on the left side.
To do this, you should add \( 3.41 \) to both sides of the equation:
\[ x - 3.41 + 3.41 = -19 + 3.41 \]
This simplifies to:
\[ x = -15.59 \]
So, the operation you should do to both sides is add 3.41.