Answer
$7\sqrt{2}$
Work Step by Step
Simplify each radical, when needed, to have:
$=7\sqrt{2}-8\sqrt{9(2)} + 4\sqrt{36(2)}
\\=7\sqrt{2} - 8\cdot 3\sqrt{2} + 4\cdot 6\sqrt{2}
\\=7\sqrt{2} - 24\sqrt{2} + 24\sqrt{2}$
Combine like terms to have:
$=(7-24+24)\sqrt{2}
\\=7\sqrt{2}$
