Question

 state if (2.5,1.5,4) could possibily be the lengths of the sides of a triangle

Answer 1

If the sum of the other 2 sides is not longer than the longest side then it can not form a triangle.

longest side = 4
sum of other two sides = 2.5+1.5= 4 which doesn't exceed the longest side.

hence the lengths can't form a triangle.

Answer 2

No..... If you've read triangle inequalities that sum of any two sides of a triangle should be greater than the remaining side. But here we've
                                                                                2.5+1.5=4
It doesn't exceed the third side therefore such a triangle is not possible