5/7*(21/20- 7/30)+16/21:8/7
5/7 * (21/20 - 7/30) + 16/21 : 8/7 = 1 1/4 1) 21/20 - 7/30 = 63/60 - 14/60 = 49/60 2) 5/7 * 49/60 = (1*7)/(1*12) = 7/12 3) 16/21 : 8/7 = 16/21 * 7/8 = (2*1)/(3*1) = 2/3 4) 7/12 + 2/3 = 7/12 + 8/12 = 15/12 = 1 3/12 = 1 1/4
1) 21/20=1,05 7/30=0,2 1,05-0,23=0,82 2) 5/7= 0,7 0,7*0,8= 0,56 3) 16/21:8/7= 14/24=0,5 4) 0,56*0,5= 0,28 ответ: 0,28