`a)\frac{4}{7}+\frac{3}{5}-\frac{1}{35}`
`=\frac{4xx5}{7xx5}+\frac{3xx7}{5xx7}-\frac{1}{35}`
`=\frac{20}{35}+\frac{21}{35}-\frac{1}{35}`
`=\frac{20+21-1}{35}`
`=\frac{40}{35}`
`=\frac{40:5}{35:5}`
`=\frac{8}{7}`
`b)\frac{2}{8}:\frac{4}{5}xx\frac{2}{7}`
`=\frac{2}{8}xx\frac{5}{4}xx\frac{2}{7}`
`=\frac{2xx5xx2}{8xx4xx7}`
`=\frac{20}{224}`
`=\frac{20:4}{224:4}`
`=\frac{5}{56}`
`c)\frac{2}{9}xx\frac{1}{7}-\frac{3}{2}`
`=\frac{2xx1}{9xx7}-\frac{3}{2}`
`=\frac{2}{63}-\frac{3}{2}`
`=\frac{2xx2}{63xx2}-\frac{3xx63}{2xx63}`
`=\frac{4}{126}-\frac{189}{126}`
`=-\frac{185}{126}`
