My answer is AUB=[-1;6[ Is it correct?

Your answer is correct, Gundegma. You can always draw a number line to help you visualize:

-3 -2 -1 0 1 2 3 4 5 6 7 8 9

<--|-----|-----|-----|-----|-----|-----|-----|-----|-----|-----|-----|-----|-->

[===============] [-1,3]

[===============] [2.6]

[===========================] [-1,3]U[2,6] = [-1,6]

Another way to think of it is that the union operation (U) combines the two sets into one set, so it includes all numbers between -1 and 6.

## Comments

[-1,6] and [-1,6[ are they same?