Answer:
Explanation:
If the lengths of two sides of a triangle are given the third side must be less than the sum of those two sides, but more than the value of the difference between the given two sides.
So for #9, the answer is 4 (which is 12-8) <x<16 (which is 12+8)
#10. 10<x<16
#11. 19<x<61
#12. 6<x<16
Below are what would happen if the 3rd side was too big (left) or too small (right)