Answer:
18
Step-by-step explanation:
it is a fundamental principle that sum of any two sides must be greater than third side
since sum of given sides is 10+7 = 17
hence any number greater than 17 for example 18 can be third side but confirm it with other sides
18 +10 is greater than 7 also 18+7 is greater than 10
hence other side can be 18
