Two sides of a triangle have lengths 10 and 18. which inequalities describe the values that possible lengths for the third side?

Well I don't know where inequalities would come in but the third length would be solved as follows.
a^2+b^2=c^2
10^2+18^2=424


Answer;
I hope this is correct, its what I would do if I had this equation.

Main idea on left, details on right