\( \sqrt{60x} = \sqrt{4} * \sqrt{15x} = 2\sqrt{15x}\)
\(\sqrt{12x} = \sqrt{4} * \sqrt{3x} = 2\sqrt{3x}\)
\(\sqrt{63x} = \sqrt{9} * \sqrt{7x} = 3\sqrt{7x}\)
\(\sqrt{42x} = \sqrt{42x}\)
Now, multiply all the radicals and you get \(252x^2 \sqrt 30\).
I think...