Again, two questions in one. Please help wherever you can

Subject: geometryneed with 6 and 7

The lengths of two sides of a triangle are 9 and 15. what can be said about the length of the third side? a. it must be greater than or equal to 6 and less than 24. b. it must be greater than or equal to 6 and at most 24. c. it must be greater than 6 and less than 24. d. it must be greater than 6 and at most 24.

Astudent is solving a system of equations by substitution and comes up with the solution 3 = 3. assuming that he solved the problem correctly, which of the following can be said about this system of equations?