Try to think how to construct a triangle where the third side is 2 cm. You won't be able to because it won't reach. (You can think of drawing the 6 cm side on paper, and then placing the point of a compass at one endpoint, and tracing a circle of radius 4 cm. Then do the same on the other end with 2 cm. You can see they won't intersect to form a triangle, only a "degenerate triangle" which is a line segment.)

Similarly, you won't be able to construct a triangle when the third side length is 10.

So it's 2 < x < 10.