x^2 - 5x + 6 =< 0

First let us factor:

(x-3)(x-2) =< 0

Then we have two cases:

case 1:

x-3 =< 0 and x-2 => 0

x =< 3 and x => 2

==>** x = [ 2, 3] **

case 2:

x-3 => 0 and x-2 =< 0

==> x => 3 and x =< 2 (impossible)

then the solution is:

**x = [2, 3]**