A:10,20,30,40,50,60,70,80,90
B:1/6,2/6,3/6,4/6,5/6
C:7/7,7/8,7/9,7/10...
2х * 0,25 = 64
0,5х = 64
х = 64 : 0,5
х = 128
3х * 8 2/17 = 1 11/23
3х * 138/17 = 34/23
3х = 34/23 : 138/17
3х = 34/23 * 17/138
3х = (17*17)/(23*69)
3х = 289/1587
х = 289/1587 : 3
х = 289/1587 * 1/3
х = 289/4761
Поправка ко второму уравнению: 3х : 8 2/17 = 1 11/23
3х : 138/17 = 34/23
3х = 34/23 * 138/17
3х = (2*6)/(1*1)
3х = 12
х = 12 : 3
х = 4
5а+3(2-a)=5a+3*2-3*a=5a+6-3a=2a+6
7.4(a+b)+0.5(a-b)=7.4a+7.4b+0.5a-0.5b=7.9a+6.9b
3(2a+1)+2(3a+1)=6a+3+6a+2=12a+5
285-(х:14-481)=36*6
285-(х:14-481)=216
х:14-481=285-216
х:14-481=69
х:14=69+481
х:14=550
х=550×14
х=7700
Проверка:
(285-(7700÷14-481)):6=36
7700÷14=550
550-481=69
285-69=216
216:6=36
36=36