中一math

7/1 x y-12/7 = 20-y

y-12/7 = 140-7y

8y = 152

152/8 = 19

y=19

________________
12-y/2 = y+16/5
....into...
60-5y/10=2y+32/10

60-5y= 2y + 32

7y = 28

y= 4
___________________________
y-5/2 = 6y/7
....into....
7y-35 = 12y

12y-7y = -35

5y = -35

y = -7

y-12/7=20-y
7y-12=140-7y....同乘7
14y-12=140
14y=152
y=76/7
12-y/2=y+16/5
120-5y=10y+32....同乘10
15y=88
y=88/15
y-5/2-6y/7=0
14y-35-12y=0....同乘14
2y=35
y=35/2