`a) 13/37 . 5/12 - 7/37 . 13/6 + (-1/37) . 13/4`
`= 13/37 . 5/12 - 13/37 . 7/6 + 13/37 . (-1/4)`
`= 13/37 . [5/12 - 7/6 + (-1/4)]`
`= 13/37 . (-1)`
`= -13/37.`
`b) 18 13/15 - 36 29/30 + 19 1/10`
`= (18 - 36 + 19) + (13/15 - 29/30 + 1/10)`
`= 1 + 0`
`= 1.`