The  points are A(1, 1, 2), B(3, 2, 4) and  C(7, 5, 6) are-

Non-collinear

the given points are A(1, 1, 2), B(3, 2, 4) and  C(7, 5, 6)

We know that the direction ratios of the line joining the points (x₁,y₁,z₁) and (x₂,y₂,z₂) are given by (x₂-x₁), (y₂-y₁) and (z₂-z₁) 

The direction ratio of AB are (3-1), (2-1) and (4-2) i.e. 2, 1 and 2

The direction ratio of BC are (7- 3), (5-2) and (6-4) i.e. 4,3 and 2

It can be seen that the direction ratios of BC are not a multiple  of AB i.e. they are not proportional.

 So points A, B and C are non-collinear.