Đáp án:
Bài 1:
a, `2/3 + 1/5 . 10/7`
` = 2/3 + 2/7`
` = 14/21 + 6/21`
` = 20/21`
b, `-3/7 + 15/26 + (-2/13 + 3/7)`
` = -3/7 + 15/26 - 2/13 + 3/7`
` = (-3/7 + 3/7) + 15/26 - 4/26`
` = 11/26`
c, `-5/9 + 5/9 : (3 1/3 - 1 2/3)`
` = -5/9 + 5/9 : (10/3 - 5/3)`
` = -5/9 + 5/9 : 5/3`
` =-5/9 + 1/3`
` = -2/9`
d, `-4/5 . 11/13 + 4/5 . -2/13 - 1/5`
` = -4/5 . (11/13 + 2/13) - 1/5`
` = -4/5 - 1/5`
` = -1`
Bài 2:
a, `x - 3/5 = -7/10`
` x = -7/10 + 3/5`
` x = -1/10`
b, `x : 19/13 = 13/5`
` x = 13/5 . 19/13`
` x = 19/5`
c, `2/9 - 7/8 . x = 1/3`
`7/8x = 2/9 - 1/3`
` 7/8 x = -1/9`
` x = -1/9 : 7/8`
` x = -8/63`
d, `2/3 x - 3/2(x - 1/2) = 5/12`
` 2/3x - 3/2x + 3/4 = 5/12`
` x(2/3 - 3/2) = 5/12 - 3/4`
` -5/6 x = -1/3`
` x = -1/3 : -5/6`
` x = 2/5`