`c, 6 1/5 . (-2/7) +14 4/5 . (-2/7)`
= `(-2/7) . ( 6 1/5 + 14 4/5 )`
= `(-2/7) . ( 6 + 14 + 1/5 + 4/5 )`
= `(-2/7) . 21`
= `-6`
`d, 7 1/6 . (-7/6) + 10 5/6 . (-7/6)`
= `(-7/6) . ( 7 1/6 + 10 5/6 )`
= `(-7/6) . ( 7 + 10 + 1/6 + 5/6 )`
= `(-7/6) . 18`
= `-21`
`e, 5/7 . 5/11 + 5/7 . 2/11 - 5/7 . 14/11`
= `5/7 . ( 5/11 + 2/11 - 14/11 )`
= `5/7 . (-7/11)`
= `-5/11`