Đáp án:
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`A = 49 8/23- (5 7/32 + 14 8/23)`
`↔ A = 49 8/23 - 5 7/32 - 14 8/23`
`↔A= (49 8/23 - 14 8/23) - 5 7/32`
`↔A=35 - 167/32`
`↔A=953/32`
Vậy `A = 953/32`
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`B = 71 38/45 - (43 8/45 - 1 17/57)`
`↔ B = 71 38/45 - 43 8/45 + 1 17/57`
`↔ B = 71 + 38/45 - 43 - 8/45 + 74/57`
`↔B = (71 - 43) + (38/45 - 8/45) + 74/57`
`↔B=28 + 2/3 + 74/57`
`↔B=86/3 + 74/57`
`↔B=1708/57`
Vậy `B=1708/57`
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`C= (-3)/7 × 5/9 + 4/9 × (-3)/7 + 2 3/7`
`↔ C = (-3)/7 × (5/9 + 4/9) + 17/7`
`↔ C = (-3)/7 × 1 + 17/7`
`↔C=(-3)/7 + 17/7`
`↔C=2`
Vậy `C=2`
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`D = (19 5/8 ÷ 7/12 - 13 1/4 ÷ 7/12) × 4/5`
`↔ D = (157/8 × 12/7 - 53/4 × 12/7) × 4/5`
`↔ D= (157/8 - 53/4) × 12/7 × 4/5`
`↔ D =51/8 ×12/7 × 4/5`
`↔D=153/14 × 4/5`
`↔D=306/35`
Vậy `D=306/35`
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`E=0,7 × 2 2/3 × 20 × 0,375 × 5/28`
`↔E = 7/10 × 8/3 × 20 × 3/8 × 5/28`
`↔ D = (7/10 × 20) × (8/3 × 3/8) × 5/28`
`↔D=14 × 1 × 5/28`
`↔D=14×5/28`
`↔D=5/2`
Vậy `D=5/2`
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`F = (9,75 × 21 3/7 + 39/4 × 18 4/7) × 15/78`
`↔ F = (39/4 × 150/7 + 39/4 × 130/7) × 15/78`
`↔ F = (150/7 + 130/7) × 39/4 × 15/78`
`↔ F=40 × 39/4 × 15/78`
`↔F=390 × 15/78`
`↔F=75`
Vậy `F=75`
