3/7-1/4 х=5 3/7-4х.
3/7- 5 3/7= -4x+1/4x
3/7-38/7= -16x/4 + x/4
-35/7=-15x/4
-15x/4= -5
x= 5*4/15
x= 4/3= 1 1/3