請問呢幾條方程點計呀?

1. y-1 over 2 = (y+1 over 3)+1
(y-1)/2 = [(y+1)/3]+1
(y-1-2)/2 = (y+1)/3
3(y-3) = 2(y+1)
3y - 9 = 2y + 2
y = 11
2. 7u-(4u-1 over 2) =21
7u - (4u-1)/12 = 21
84u - 4u + 1 = 252
80u = 251
u = 251/80
3. t+13 over 5 =(1 over 5)-(t+5 over 2)
(t+13)/5 = (1/5) - (t+5)/2
2t + 26 = 2 - 5t - 25
7t = -49
t = -7
4. (2-t over 4)-t = 2t-3 over 5
(2-t)/4 - t = (2t-3)/5
10 - 5t - 20t = 8t - 12
33t = 22
t = 2/3