I guess you could do this sort of quesion by raising the numbers to a power until they are whole numbers and then working it out.
Raising the first one by squaring it gives
6∗9,100,49∗2=54,100,98
therefore the result would be
3√6,7√2,10
for the second one squaring it would be
−4∗3,−16,−9∗2,−4∗72=−12,−16,−18,−14
so it is
−3√2,−4,−2√72,−2√3
(note that I changed to negative because of that)
for the third one you need to cube it
21,27∗2,21.952,8∗5=21,54,21.952,40
Then it becomes
3√21,2.8,23√5,33√2
(Sorry for errors, I kind of rushed it)