Đáp án:
$\\$
Bài `1`
`a,`
`(-0,75 + 1/2) ÷ 4/3`
`= (-1)/4 × 3/4`
`= (-3)/16`
$\\$
`b,`
`5/9 × 2/7 + 5/9 × 5/7 - 8/3`
`= 5/9 × (2/7 + 5/7) - 8/3`
`= 5/9 × 1 - 8/3`
`= 5/9 - 8/3`
`= (-19)/9`
$\\$
`c,`
`7,5 × 1 3/4 - 6 2/5`
`= 7,5 × 7/4 - 32/5`
`= 105/8 - 32/5`
`= 269/40`
$\\$
Bài `2`
`a,`
`x + 5/12 = -1 2/7`
`-> x + 5/12 = (-9)/7`
`-> x = (-9)/7 - 5/12`
`-> x = (-143)/84`
Vậy `x=(-143)/84`
$\\$
`b,`
`4 1/2 x ÷ 5/12 = 0,5`
`-> 9/2x = 0,5 × 5/12`
`-> 9/2x =5/24`
`-> x = 5/24 ÷ 9/2`
`-> x = 5/108`
Vậy `x=5/108`
$\\$
`c,`
`7,5 × 1 3/4x = 6 2/5`
`-> 7,5 × 7/4x = 32/5`
`-> 7/4x = 32/5 ÷ 7,5`
`-> 7/4x = 64/75`
`-> x= 64/75 ÷ 7/4`
`-> x = 256/525`
Vậy ` x = 256/525`
