x - 1/2x - 1/4x -1/7x = 3
или
x - 0.5x - 0.25x - 1/7x = 3

x - 1/2x - 1/4x -1/7x = 3 х-14/28х-7/28х-4/28х=3х-25/28х=328/28х-25/28х=33/28х=3х=3:3/28х=3*28/3х=28