Carlos made an error in the step where he added \(-18\) and \(52\).
In his solution, he correctly starts with the equation:
\[ 14x - 52 = -18 \]
When he adds \(52\) to both sides, he gets:
\[ 14x = -18 + 52 \]
However, the correct calculation for \(-18 + 52\) should be:
\[-18 + 52 = 34,\]
not \(218\) as he claimed.
So the correct answer is:
He incorrectly added \(-18\) and \(52\).