We want to know how many brownmies did Fred and his family eat together.
We will call to the total of the brownies by 1. On this case, after Fred ate 1/3 of the brownies, he will have:
[tex]1-\frac{1}{3}=\frac{3-1}{3}=\frac{2}{3}[/tex]This means that he has left 2/3 of the brownies. After his family ate 1/6 of the brownies:
[tex]\frac{2}{3}-\frac{1}{6}=\frac{4}{6}-\frac{1}{6}=\frac{3}{6}=\frac{1}{2}[/tex]This means they will have left 1/2 of the tray of brownies, and that they ate half of it.
