Đáp án:
`7,`
`75% - 1 1/2 + 0,5 ÷ 5/12`
`= 3/4 - 3/2 + 0,5 × 12/5`
`= 3/4 - 3/2 + 6/5`
`= 15/20 - 30/20 + 24/20`
`= (15 - 30 + 24)/20`
`= 9/20`
$\\$
`8,`
`1,4 × 15/49 - (4/5 + 2/3) ÷ 2 1/5`
`= 3/7 - 22/15 ÷ 11/5`
`= 3/7 - 22/15 × 5/11`
`= 3/7 - 2/3`
`= 9/21 - 14/21`
`= (9 - 14)/21`
`= (-5)/21`
$\\$
`9,`
`0,25 × 2 1/3 × 30 × 0,5 × 8/45`
`= 1/4 × 7/3 × 30 × 1/2 × 8/45`
`= (1 × 7 × 30 × 1 × 8)/(4 × 3 × 1 × 2 × 45)`
`= 1680/1080`
`= 14/9`
$\\$
`10,`
`3/7 × (5/8 - 7/9) - 5/8 × (3/7 - 8/15)`
`= 3/7 × 5/8 - 3/7 × 7/9 - 5/8 × 3/7 + 5/8 × 8/15`
`= [3/7 × 5/8 - 5/8 × 3/7] + [-3/7 × 7/9 + 5/8 × 8/15]`
`= [5/8 × (3/7 - 3/7)] + [(-1)/3 + 1/3]`
`= [5/8 ×0] + 0`
`= 0+0`
`= 0`
