设这批水果共有x千克,180+(x-180)× 2 7 = 1 2 x, 180+ 2 7 x-180× 2 7 = 1 2 x, 180-180× 2 7 = 1 2 x- 2 7 x, 900 7 = 3 14 x, 900 7 ÷ 3 14 = 3 14 x÷ 3 14 , x=600;答:这批水果有600千克.故答案为:600.