Now we substitute these simplified terms back into the original expression:
\[
7 \cdot 4 \sqrt{2} \sqrt{x} - 5 \cdot 3 \sqrt{2} \sqrt{x}
\]
This simplifies to:
\[
28 \sqrt{2} \sqrt{x} - 15 \sqrt{2} \sqrt{x}
\]
Step 4: Combine Like Terms
Now we combine the like terms:
\[
(28 - 15) \sqrt{2} \sqrt{x} = 13 \sqrt{2} \sqrt{x}
\]
Final Answer
Thus, the final simplified expression is:
\[
\boxed{13 \sqrt{2} \sqrt{x}}
\]