Đáp án:
a) x + 1/3 = 3/4 b) x - 2/5 = 5/7
x = 3/4 - 1/3 x = 5/7 + 2/5
x = 9/12 - 4/12 x = 25/35 + 14/35
x = 5/12 x = 39/35
c) -x - 2/3 = -6/7 d) 4/7 - x = 1/3
-x =( -6/7 ) + 2/3 x = 4/7 - 1/3
- x = (-18/21) + 14/21 x = 12/21 - 7/21
- x = - 4/21 x = 5/21
x = 4/21