а)9/56-(7/15-5/12)*(3/14+1/2)=

а) 9/56 - (7/15 - 5/12) * (3/14 + 1/2) = 1/81) 7/15 - 5/12 = 28/60 - 25/60 = 3/60 = 1/202) 3/14 + 1/2 = 3/14 + 7/14 = 10/14 = 5/73) 1/20 * 5/7 = (1*1)/(4*7) = 1/284) 9/56 - 1/28 = 9/56 - 2/56 = 7/56 = 1/8