Drag each set of side lengths to show whether they can or cannot make a triangle, or if there is not enough information to tell. click on the link given

The conditions for existence of a triangle are as follows:
i. Condition on sides
According to the triangle inequality, the sum of lengths of any two sides of a triangle must be greater than of equal to the length of the third side. A triangle with three positive side lengths exists if those side lengths satisfy the triangle inequality.
Using this condition we can justify if the given dimensions can form triangles or not as follows:
a] 4 ft, 6 ft, 11 ft
the sum of short side is (4+6)=10 which is less than the sum of the longest side. Therefore we conclude that the three lengths CANNOT make a triangle:
CANNOT make a triangle

b] 5 ft, 7 ft, 11 ft
sum of shorter sides is (5+7)=12
since 12 is greater than 11, then the three length can make a triangle.
CAN make a triangle

c] 7 ft, 8 ft, 14 ft
The sum of shorter side is:
(7+8)=15 ft
since the sum of shorter side is longer than that of the longer side, we conclude that the three lengths can form a triangle. 
CAN make a triangle