数学题 12-(9-y)=5(y-4)-7(7-y)

12-(9-y)=5(y-4)-7(7-y)
12-9+y=5y-20-49+7y
3+y=12y-69
11y=72
y=72/11

12-(9-y)=5(y-4)-7(7-y)
12-9+y=5y-20-49+7y
7y+5y-y=12-9+20+49
11y=72
y=72/11

12-9+y=5y-20-49+7y
y-5y-7y=-20-49-12+9
-11y=-32
y=32/11

12-(9-y)=5(y-4)-7(7-y)
12-9+y=5y-20-49+7y
y-5y-7y=-20-49+9-12
-11y=-66
y=66/11
y=6

12-(9-y)=5(y-4)-7(7-y)
12-9+y=5y-20-49+7y
5y+7y-y=12-9+20+49
11y=72
y=72/11
y=11 分之72