Answer:
1: 11√3 - 7√6
2: 11√3 - 7√6
3: -9
4:12
Step-by-step explanation:
To add radicals they need to have the same radical part for the first one we have
7√3- 4√6 + √48 - √54
We can simplify the last two into 4√3 and 3√6
So we have 7√3 - 4√6 + 4√3 - 3√6
adding similar radicals we get
11√3 - 7√6
For the second one we have 11√3 - 7√6
There's nothing we can do from here so keep that as your answer
This one is quite easy -3√9
square root of 9 is 3
so we have -3*3 which is -9
next is
4√9
same deal as the one before
3*4=12
, you have to factor it as 
, not 
, because that will leave an extra 6x because of 8x - 2x.