Answer:
(15, 26, 42)
Explanation:
Sides of a triangle rule: the sum of the lengths of any two sides of a triangle has to be greater than the length of the third side.
(8, 1, 18)
8 + 11 = 19 > 18
11 + 18 = 29 > 8
8 + 18 = 26 > 11
Therefore, this is a triangle
(6, 9, 12)
6 + 9 = 15 > 12
6 + 12 = 18 > 9
9 + 12 = 21 > 6
Therefore, this is a triangle
(15, 26, 42)
15 + 26 = 41 < 42
15 + 42 = 57 > 26
26 + 42 = 68 > 15
Therefore, this is NOT a triangle
(13, 19, 31)
13 + 19 = 32 > 31
13 + 31 = 44 > 19
19 + 31 = 50 > 13
Therefore, this is a triangle