а) (3/4-12)×5 б) (5/7+1/21):2 в) (7/10-1/5):3 г) 1/4-1/12)×5 д) (1/4+1/6)×10 е) (5/6-15):7

а) (3/4-12)×5  = -11 1/4 * 5 = - 56 1/4б) (5/7+1/21):2 = (15/21 + 1/21):2=16/21 :2 = 8/21в) (7/10-1/5):3 = (7/10 - 2/10):3 = 1/2:3 = 1/6г) (1/4-1/12)×5 = (3/12 - 1/12)*5 = 1/6 * 5 = 5/6д) (1/4+1/6)×10 = (3/12 + 2/12)*10 = 5/12 * 10 = 4 1/6е) (5/6-15):7 = -14 1/6 : 7 = - 2 1/42