An acute triangle has sides measuring 10 cm and 16 cm. the length of the third side is unknown.

which best describes the range of possible values for the third side of the triangle?

x < 12.5, x > 18.9
12.5 < x < 18.9
x < 6, x > 26
6 < x < 26

So because we know that the 3rd side of a triangle not can being less than the difference of the first and second sides and so not can being greater than the sum of the first and second sides so from these result that the last one choice will be right sure 

6 < x < 26

If you make you answer for clear i can answer it : )