Tic Tac Toe - culture fair IQ test

This is pretty strong IQ test, capable to estimate IQ up to 170 sd=15, which is 1/650.000 rarity. The test is mainly numerical.
Each solution should be given using only characters 'x' (ASCII code 120) or 'o' (ASCII code 111), without spaces. There are no empty solutions.
Hint: If you find more than one logical solution to a particular item, you must choose the most logical one.
Important: You will receive the most accurate score if you try the test no more than twice.

1) x xxxx xxxxxxxxx


2) o oo xxx oooo ooooo


3) x o, oo x, xx ooo, ooooo


4) xxx xx ooooo, x oooooo


5) o oooo xxx, oo ooooo


6) xxxx, oxxxxxx, xxxxx ooxxxxx, xxxxxx


7) xxooo


8) xoxxooxxxo


9) xooxxxo


10) xoo xxxoooo xx
11) x xx   xxxxxxxx


12) xox   xox


13) ox oxo   xoxox


14) ooo oox oxo xoo   xxo


15) xxxxx xxx x   ooo


16) x ox xox   xxxox


17) x xxx xxxx   ox


18) xxxxxooooo xxxxooo xxxo   ooox


19) xxxx xxxxxxxx   oooxx


20) xxxxx xxx x