`***`Lời giải`***`
a)
`(\frac{9}{25}-2.18):(3\frac{4}{5} +0,2)`
`=(\frac{9}{25}-36):(\frac{19}{5} +0,2)`
`=\frac{9-900}{25}:\frac{19+1}{5}`
`=\frac{-891}{25}:\frac{20}{5}`
`=\frac{-891}{25}:4`
`=\frac{-891}{25}. 1/4`
`=\frac{-891}{100}`
b)
`\frac{3}{8}.19\frac{1}{3}-\frac{3}{8}.33\frac{1}{3}`
`=\frac{3}{8}.(19\frac{1}{3}-33\frac{1}{3})`
`=\frac{3}{8}.(\frac{58}{3}-\frac{100}{3})`
`=\frac{3}{8}.\frac{-42}{3}`
`=\frac{3}{8}.-14`
`=-42/8`
`=-21/4`
c)
`1\frac{4}{23}+\frac{5}{21}-\frac{4}{23}+0,5+\frac{16}{21} `
`=\frac{27}{23}+\frac{5}{21}-\frac{4}{23}+1/2+\frac{16}{21} `
`=(\frac{27}{23}-\frac{4}{23})+(\frac{5}{21}+\frac{16}{21})+1/2 `
`=\frac{23}{23}+\frac{21}{21}+1/2 `
`=1+1+1/2 `
`=2+1/2 `
`=\frac{4+1}{2}`
`=5/2`
