Jawab nomor 5,6, dan 7 Pake caranya kalau bisa? Please!!!!

yg no 5 dijelasin donk

5.
[tex] \sqrt{180} - 3 \sqrt{80} + \sqrt{245} \\ = 6 \sqrt{5} - 12 \sqrt{5} + 7 \sqrt{5} \\ = \sqrt{5} [/tex]