(1)试判断a,b,c的正负性;
(2)根据数轴化简:
①|a|=_____; ②|b|=_____:
③|c|=_____; ④|-a|=_____;
⑤|-b|=_____; ⑥|-c|=_____.
(3)若|a|=5.5,|b|=2.5,|c|=5,求a,b,c的值.