Answer: 37 (side AB)
Explanation:
For this question you would have to use Pythagoras' theorem. Pythagoras' theorem states that c²=a²+b².
so when you put the numbers in the formula you get c²=12²+35²
12²=144
35²=1225
c²=144+1225
c²=1369
Then because you want c on it's own you square root 1369.
c=√1369
c=37
Hope this helps :)