Answer:
large box = 3 feet, small box = 1 foot
Explanation:
large box = l
small box = s
3l + 2s = 11
2l + 1s = 7
This is simultaneous equations
so you make the one of the boxes equal
I am going to make the small boxes equal each other
4l + 2s = 14
3l + 2s = 11
Take them both away from each other
1l = 3
put that back into the equation
so s = 1