Step-by-step explanation:

1 - 1/3 = ?

Because it was one whole when the mother baked it and the she left 1/3 for the father

BUT

What part of the cake was for her children?

There are one 1/3 in the cake(one whole/1)  

Thats whats left for the father

But the question is what part is for the children?

I searched and there are three 1/3 in one whole/1

So the father was left with 1/3 of cake(one whole/1)

1/3 + 1/3 = 2/3

2/3 I THINK is the answer

Ur gonna do the rest I'm too lazy unu