[tex]\it x=\sqrt{49}-3\sqrt{20}+\sqrt{28}=7-3\sqrt{4\cdot5}+\sqrt{4\cdot7}=7-6\sqrt5+2\sqrt7\\ \\ y=\sqrt{180}-\sqrt{112}+\sqrt{64}=\sqrt{36\cdot5}-\sqrt{16\cdot7}+8=6\sqrt5-4\sqrt7+8[/tex]
[tex]\it x+y= 7-6\sqrt5+2\sqrt7+6\sqrt5-4\sqrt7+8=15-2\sqrt7\\ \\ x-y= 7-6\sqrt5+2\sqrt7-6\sqrt5+4\sqrt7-8=-1-12\sqrt5+6\sqrt7[/tex]
