1.1/5x-1/4x=3,x=-27
2.2/3x=4/9*5/7,x=10/21
3.12+2/5x=30,x=45
4.[2/3+（1/4除以3/4）]=1/4
5.x除以1/5+1/2=9/2(四又二分之一),x=4/5
6.7/3除以x=9/11*11/13,x=9/7
7.1/3x=4/5*5/7,x=12/7
8.x+4=7/4*4,x=3
9.x-3/4=1/2*2/3,x=13/12
10.3/4*5/6-2=11/8
11.5/18x=20,x=72,7/12*72=42
12.2/3x=60,x=90,7/9*90=70
13.3/5x=48,x=80,7/8*80=70.
14.24*7/8-2/7x=7,x=49
15.3/4x-60=12,x=96
16.36+36*4/9=42
17.30*7/5=42
18.设甲为x,则乙为6/5x,x+6/5x=66,x=30,乙为66-30=36.所以它们的差是36-30=6
19.8/13除以7+1/7*6/13=14/91