Tentukan hasil dari : a ) 2/15 - 1/2 + 3/10 b ) 3/7 + 4/21 - 13/14 Tolong dijawab dengan cara!

a) 2/15 - 1/2 + 3/10
  = 4/30 - 15/30 + 9/30
  = -11/30 + 9/30
  = -2/30
  = - 1/15
b) 3/7 + 4/21 - 13/14
  = 18/42+ 8/42 - 39/42
  = 26/42 - 39/42
  = - 13/42
  = -1/3