Answer:
A yes, B no
Step-by-step explanation:
The triangle inequality states that the sum of any 2 sides of the triangle must be greater than the third side.
A Given 21, 18, 17 , then
21 + 18 = 39 > 17
21 + 17 = 38 > 18
18 + 17 = 35 > 21
Thus the triangle could exist
B Given 3, 12, 8 , then
3 + 12 = 9 > 8
3 + 8 = 11 < 12 ← fails the test
Thus the triangle does not exist
