1)5 7/13+2 6/13=8
2)5 1/4-3 3/4=1 1/2
3)22:8=2 3/4
4)1 1/2:5=3/10
5)2 3/4-3/10=2 9/20
<span>3,5(3-4b)-5,7+8b,при б=1,3
10,5-14</span>b-5,7+8b=4,8-6<span>b=4,8-6*1,3=4,8-7,8=-3</span>
1.000 - (285 - х) = 820
1.000 - 285 + х = 820
715 + х = 820
х = 820 - 715
х = 105
<u>проверка:</u>
1.000 - (285 - 105) = 820
1.000 - 180 = 820
820 = 820