Math 高手救下我/.\

1. (y+5)/2 - y/7 = 0
7(y+5)/14 - 2y/14 = 0
7y+35-2y / 14 = 0
7y - 2y = -35
y = -7
2. s+7/2 - 3s/8 = 11
4(s+7)/8 - 3s/8 = 88/8
4s+28-3s /8= 88/8
s + 28 = 88
s = 60
3. 3s+4/5 = 2s+7/3
3(3s+4) / 15 = 5(2s+7) / 15
9s+12 / 15 = 10s+35 /15
9s + 12 = 10s + 35
-s = 35 - 12
s = -23
4. 3t - t-6/12 = 18
36t/12 - t-6/12 = 18
36t -(t-6) / 12 = 18
35t + 6 / 12 = 18
35t + 6 = 216
35t = 210
t = 6
5. 1/12 + 1/v = 4
1/v = 4 - 1/12
1/v = 47/12
v = 12/47