`1)`
`a) (3/8 + \frac{-3}{4} + 7/12) : 5/6 + 1/2`
`= (9/24 +\frac{-18}{24}+ 14/24) . 6/5 + 1/2`
`= 5/24 . 6/5 + 1/2`
`= 1/4 + 1/2`
`= 1/4 + 2/4`
`= 3/4`
`b) \frac{-3}{7} . 5/9 + 4/9 . \frac{-3}{7} + 2 3/7`
`= \frac{-3}{7} . ( 5/9 + 4/9) + 2 3/7`
`= \frac{-3}{7} . 1 + 2 3/7`
`= \frac{-3}{7} + 2 3/7`
`= 2`
`2)`
`a) 2/3 x - 1/2 x = 5/12`
`(2/3 - 1/2) x = 5/12`
`(4/6 - 3/6) x = 5/12`
`1/6 x = 5/12`
`x = 5/12 : 1/6`
`x = 5/2`
`b)(2 4/5 x - 50) : 2/3 = 51`
`(14/5 x - 50) = 51 . 2/3`
`14/5 x - 50 = 34`
`14/5x = 34 + 50`
`14/5x = 84`
`x = 84 : 14/5`
`x = 30`
