Each carton has 6 eggs, use it as a conversion factor (1carton/6eggs), to find how many cartons the baker would need to have 225 eggs:
[tex]225eggs\cdot\frac{1carton}{6eggs}=37.5cartons[/tex]The baker would need 37.5 cartoons, but, as he can't order 37.5 cartons, he needs to order 38 cartons.