8у-6у+9=7-10у-10
12у=-12
У=-1
1)
х + 7 = 61
х = 61 - 7
х = 54
<u>проверка:</u>
54 + 7 = 61
61 = 61
2)
56 - х = 9
- х = 9 - 56
- х = - 47
х = 47
<u>проверка:</u>
56 - 47 = 9
9 = 9
3)
х - 11 = 39
х = 39 + 11
х = 50
<u>проверка:</u>
50 - 11 = 39
39 = 39
<span>(6 7/12-3 17/36)*1/2-4 1/3:13/20=
=(6 21/36 - 3 17/36) *1/2 - 13/3 * 20/13 = 3 4/36 *1/2 - 20/3 =
=3 1/9 *1/2 - 20/3 = 28/9 *1/2 - 20/3 = 14/9 - 20/3 = 14/9 - 60/9= -46/9=
=-5 1/9</span>
6*3=18.......................