6-[1-( 1 12 + 1 15 )×6]÷ 1 10 =6-[1-( 5 60 + 4 60 )×6]÷ 1 10 =6-[1- 9 60 ×6]÷ 1 10 =6- 1 10 ÷ 1 10 =6-1=5(天);答:乙、丙两队又共同合修了5天才完成.