(1-7/10)х = 2 1/4
х - 7/10 х = 9/4
3/10 х = 9/4
х = 9/4 : 3/10 = 9/4 * 10/3 = 15/2 = 7 1/2
(3 1/8 + 1 3/4) х = 2 1/6
(25/8 + 7/4)х = 13/6
39/8 х = 13/6
х = 13/6 : 39/8 = 13/6 * 8/39 = 4/9
(1/4+1/5)х = 1 4/5
9/20 х = 9/5
х = 9/5 : 9/20 = 9/5 * 20/9 = 4
(2 1/12 - 1 5/6) х = 3/4
(25/12 - 11/6) х = 3/4
1/4 х = 3/4
х = 3/4 : 1/4 = 3/4 * 4/1 =3