Finding the 3rd side of a triangle's minimum and maximum length (In CM)

Question

My first side is 10 as well as my second side, I'm supposed to find the Range of the 3rd Side written as an interval. What would it be? 

Answer 1

if 2 sides are each 10

then the possible values of the 3rd side are between 0 and 20

10-10=0, 10+10=20

3rd side's interval is (0,20)