1) 1/2 a + 1/3 a - 1/4 a = (1/2 + 1/3 - 1/4) a = (6/12 + 4/12 - 3/12) a = 7/12 a = 7/12 12/7 = 1.
2) 4/7 b + 5/21 b - 2/3 b = (4/7 + 5/21 - 2/3) b = (12/21 + 5/21 - 14/21) b = 3/21 b = 3/21 21/3 = 3.
3) 1 5/12 m + 2 7/18 m - 1 2/9 m = (17/12 + 17/18 - 11/9) m = (153/108 + 102/108 - 96/108) m = 159/108 m = 53/36 36/31 = 53/31.
1) 1/2 a + 1/3 a - 1/4 a = (1/2 + 1/3 - 1/4) a = (6/12 + 4/12 - 3/12) a = 7/12 a = 7/12 12/7 = 1.
2) 4/7 b + 5/21 b - 2/3 b = (4/7 + 5/21 - 2/3) b = (12/21 + 5/21 - 14/21) b = 3/21 b = 3/21 21/3 = 3.
3) 1 5/12 m + 2 7/18 m - 1 2/9 m = (17/12 + 17/18 - 11/9) m = (153/108 + 102/108 - 96/108) m = 159/108 m = 53/36 36/31 = 53/31.