Basic Principle we will have to employ is sum of two sides is greater than the third.
One can easily get this question wrong if you try to this in your head in the exam. So i prefer to do this on a pad, because these are simple ones and freebies.
1) 3rd side would be 2 and 2 + 2 not greater than 5
2) 3rd side is 8 and 2+5 not greater than 8
3) 3rd side is 12 and 2+5 not greater than 12