(d) 22.35
\(3\sqrt5 \) + \(\sqrt{125}\) = 17.88
\(\Rightarrow\) \(3\sqrt5 \) + \(\sqrt{5^2\times5}\) = 17.88
\(\Rightarrow\) \(3\sqrt5 \) + \(5\sqrt5\) = 17.88
\(\Rightarrow\) \(8\sqrt5 \) = 17.88 \(\Rightarrow\) \(\sqrt5\) = \(\frac{17.88}{8}\) = 2.235
Now, \(\sqrt{80}+6\sqrt5\) = \(\sqrt{16\times5}\) + \(6\sqrt5\)
= \(4\sqrt5 + 6\sqrt5\) = \(10\sqrt5\)
=10 x 2.235 = 22.35.