1) (1-1/7)х=2 1/4, (7/7-1/7)х=9/4, 6/7х=9/4, х=9/4:6/7, х=9/4*7/6, х=21/8= 2 5/8
2) (1/4+1/5)х=1 4/5, (5/20+4/20)х= 9/5, 9/20х=9/5, х=9/5:9/20, х=9/5*20/9, х=4
3) (3 1/8 + 1 3/4)х=2 1/6, (25/8+7/4)х=13/6, (25/8+14/8)х=13/6, 39/8х=13/6, х=13/6:39/8, х=13/6*8/39, х=4/9
4) (2 1/12- 1 5/6)х=3/4, (25/12-11/6)х=3/4, (25/12-22/12)х=3/4, 3/12х=3/4, 1/4х= 3/4, х=3/4:1/4, х=3/4*4/1, х=3