`A=(-2 1/5 +2/7 - 12/13 ) - (-5/7 +1/13)`
`A=-11/5 + 2/7 - 12/13 +5/7 -1/13`
`A=-11/5 + (2/7 + 5/7) -(12/13 + 1/13)`
`A=-11/5 + 1-1`
`A=-11/5`
--------------------------------------------
`B=12/17 . 5/7 - -12/17 . 1/7 + 1/(17.7) . 12`
`B=12/17 . 5/7 - 12/17 . -1/7 + 12/17 . 1/7`
`B=12/17. (5/7 +1/7 +1/7)`
`B=12/17 . 1=12/17`