2 - (5/6 + 3/2 - 4)

= 12/6 - (5/6 + 9/6 - 24/6)

= 12/6 - (-10/6)

= 22/6

  (1/7 - 9/2 + 5) ÷ 1/2

= (2/14 - 63/14 + 70/14) ÷ 1/2

= 9/14 ÷ 1/2

= 9/7

  -5 + 8 × (6 - (-4) + 9)

= -5 + 8 × 19

= -5 + 152

= 147

   [(1/3 × 5/2)]/(-2/3) - 15/2

= (5/6)/(-2/3) - 15/2

= 5/6 × (-3/2) - 15/2

= -15/12 - 15/2

= -15/12 - 90/12

= -105/12

= -35/4

  1/2 - (9 - (-13) + 25)

= 1/2 -  47

= 1/2 - 94/2

= -93/2