OSDev.org

is
task 1 Base adress 0xffff1 and the limit is 0xffff
task 2 Base adress 0xffff1+0xffff1 and the limit is 0xffff
task 3 Base adress 0xffff1+0xffff1+0xffff1 and the limit is 0xffff
is like that the base adress for the next is the base adress of the
previous + limit ?

please I´m confused

Really you can lay out your memory however you like, but yes. In general, you'll pack your tasks' code together so base+limit of one task is the base of the next task. This is only the good if you're doing segmented memory. If you're doing paged memory, then you'll put each task's code on separate pages.