2.7/X=7.5
X=2.7/7.5
X=9/25
2X+4X=27
6X=27
X=27/6
X=4.5
8X-5*1.4=9.16
8X-7=9.16
8X=9.16+7
X=16.16/8
X=2.02��һ��������ʲô��