Answer
$480$ calories from snacks
Work Step by Step
Based on her statement, we know the following
$Lunch=\frac{1}{2}*Breakfast$
$Dinner=200+Breakfast$
$Snacks=Breakfast-120$
Based on the equation that $net= total - burnt$
$1480=Breakfast+Lunch+Dinner+Snack-700$
We can then substitute
Breakfast for $Snacks+120$
Lunch for $\frac{1}{2}*(Snacks+120)$
Dinner for $Snacks+320$
So the new equation is
$1480=Snacks+120+\frac{1}{2}Snacks+60+Snacks+320+Snacks-700$
Then
$1480=3.5*Snacks-200$
Solving for snacks we get 480 calories were consumed
