Đáp án:
A) `1/8`
B) `\frac{41}{36}`
C) `\frac{11}{20}`
Giải thích các bước giải:
A) `\frac{7}{20}-(5/8-2/5)`
`=\frac{7}{20}-(\frac{25}{40}-\frac{16}{40})`
`=\frac{7}{20}-\frac{9}{40}`
`=\frac{14}{40}-\frac{9}{40}`
`=\frac{5}{40}=1/8`
B ) `5/6+(5/9-1/4)`
`=5/6 + (\frac{20}{36} - \frac{9}{36})`
`=5/6 + \frac{11}{36}`
`=\frac{30}{36} + \frac{11}{36}`
`=\frac{41}{36}`
C ) `\frac{9}{10}-(2/5+\frac{3}{10}) + \frac{7}{20}`
`=\frac{9}{10}-(\frac{4}{10}+\frac{3}{10})+\frac{7}{20}`
`=\frac{9}{10}-\frac{7}{10}+\frac{7}{20}`
`=\frac{2}{10}+\frac{7}{20}`
`=\frac{4}{20}+\frac{7}{20}`
`=\frac{11}{20}`
