[tex]x = \sqrt{49} - 3 \sqrt{20} + \sqrt{28} = \\ 7 - 3 \times 2 \sqrt{5} + 2 \sqrt{7} = \\ 7 - 6 \sqrt{5} + 2 \sqrt{7} [/tex]
[tex]y = \sqrt{180} - \sqrt{112} + \sqrt{64} = \\ 6 \sqrt{5} - 4 \sqrt{7} + 8[/tex]
[tex]x + y = 7 - 6 \sqrt{5} + 2 \sqrt{7} + 6 \sqrt{5} - 4 \sqrt{7} + 8 = \\ 7 + 2 \sqrt{7} - 4 \sqrt{7} + 8 = \\ 7 - 2 \sqrt{7} + 8 =15-2 \sqrt{7}[/tex]
[tex]x - y = 7 - 6 \sqrt{5} + 2 \sqrt{7} - 6 \sqrt{5} - 4 \sqrt{7} + 8 = \\ 7 - 12 \sqrt{5} - 2 \sqrt{7} + 8 =15-12 \sqrt{5} - 2 \sqrt{7}[/tex]
