1/6:(1/4х-1/3)-3/8=1/40

1/6:(1/4х-1/3)-3/8=1/40
1/6:(1/4х-1/3)=1/40+3/8
1/6:(1/4х-1/3)=1/40+15/40
1/6:(1/4х-1/3)=2/5
1/4х-1/3=1/6:2/5
1/4х-1/3=5/12
1/4х=5/12+1/3
1/4х=5/12+4/12
1/4х=9/12
х=9/12:1/4
х=3