1/6 / (1/4 х-1/3) - 3/8=1/40

1/6 / (х/4 - 1/3) -3/8 = 1/40
1/6 (3х-4/12) - 3/8 = 1/40
1/6 * 12/3х-4 - 3/8 = 1/40
2/3х-4 - 3/8 = 1/40
2/3х-4 = 1/40 + 3/8
2/3х-4 = 16/40
3х-4 = (2*40)/16
3х-4 = 5
3х=9
х=3