Let \(x\) be the value to be subtracted. \(\therefore \sqrt{72} - x = \sqrt{32}\) i.e., \(6\sqrt{2} - x = 4\sqrt{2}\) i.e., \(x = 6\sqrt{2} - 4\sqrt{2}\) i.e., \(x = 2\sqrt{2}\) i.e., \(x = \sqrt{8}\) \(\therefore\) Subtracting \(\sqrt{8}\) from \(\sqrt{72}\) gives \(\sqrt{32}\).