I'll just do the workings,
First Vertical Row
6/2 (as you need to put the milk over the eggs) = 3/1 (simplify the fraction, both can be divided by 2)
= 3/1
Second Vertical Row
= x/3 = 3/1 (x is basically milk for the second vertical row)
= x = 3/1 x 3
= x = 9
Milk = 9
Third Vertical Row
x is the egg,
= 12 / x = 3/1 (3/1 is the same as 3)
= x= 12 / 3
= x = 4
Egg = 4