9th grade Algebra square root problems? I just dont get it..best answer gets 10 points!

I'm on the last 5 problems of my homework and none of them make sense to me.
Here they are: (and please explain how you did so)

5√7+2√7

√3+5√3

11√3-12√3

2√6-√6

4√5+√3+√5

I tried to show the steps. I hope this helped.

5√7 + 2√7 = (5 + 2)√7 = 7√7

√3 + 5√3 = (1)√3 + 5√3 = (1 + 5)√3 = 6√3

11√3 - 12√3 = (11 - 12)√3 = -1√3

2√6 - √6 = 2√6 - (1)√6 = (2 - 1)√6 = 1√6 = √6

4√5 + √3 + √5 = 4√5 + √3 + (1)√5 = (4 + 1)√5 + √3 = 5√5 + √3