We will simplify the expression step by step, starting from the innermost square root.
Step 1: Simplify the Innermost Square Root
\[
\sqrt{144} = 12 \quad \text{(since } 12 \times 12 = 144\text{)}
\]
Step 2: Substitute and Simplify the Next Level
\[
\sqrt{37 + \sqrt{144}} = \sqrt{37 + 12} = \sqrt{49} = 7 \quad \text{(since } 7 \times 7 = 49\text{)}
\]
Step 3: Simplify the Outermost Expression
\[
\sqrt{218 + \sqrt{37 + \sqrt{144}}} = \sqrt{218 + 7} = \sqrt{225} = 15 \quad \text{(since } 15 \times 15 = 225\text{)}
\]
Verification
Let's verify each step:
\begin{itemize}
\item \(\sqrt{144} = 12\) is correct as \(12^2 = 144\)
\item \(37 + 12 = 49\) and \(\sqrt{49} = 7\) are correct
\item \(218 + 7 = 225\) and \(\sqrt{225} = 15\) are correct
\end{itemize}
Final Answer
After simplifying all nested square roots, we find:
\[
K = \boxed{15}
\]