180 ÷ 2 = 90; 90 ÷ 2 = 45 ; 45 ÷ 3 = 15 ; 15 ÷ 3 = 5 ; 5 ÷ 5 = 1 => 180 = (2^2) (3^2) 5 => \(\sqrt{180} = 2*3 * \sqrt{5 }=6 \sqrt{5} ;\)
In the same way we have \(\sqrt{245}=7 \sqrt{5} ;\) and \(\sqrt{320 }=8 \sqrt{5} ;\)
Finally, \(6 \sqrt{5}+7 \sqrt{5} - 8 \sqrt{5} = 13 \sqrt{5} - 8 \sqrt{5} =7 \sqrt{5}.\)
