Answer:
Let the third side be x
We know that
Sum of two sides of a triangle must be greater than the third side
So,
9 + 3 > x
12 > x (1)
Also, difference of two side of triangle must be smaller than the third side
9 - 3 < x
6 < x (2)
From 1 and 2 we concluded
6 < x < 12
The length of third side would lie between 7 to 11
