By the equation 10-x=5+x/ 12

De: x=60/ 13

2. Set football X yuan and basketball Y yuan.

Solve equation 50x+40y = 3000；; 54.5 x+44.4y = 3298；

Get x = 32y = 35.

3. Let the alcohol content of the stock solution be X cups and the water content be Y cups.

There is an equation: x/(1+x+y) = 0.25; ( 1+x)/(2+x+y)= 0.4；

x = 1； y = 2； The content is 1/3.