I think what you have to do is add up A B and C so you know how much space they take out of the 456 cm which is the length of the wall. Then you subtract 456cm (which is the total) the length of the wall by the result you got from the addition. And then the result you get divide it by 2 so it would give you what is the width of D and E since it says they're equal.
But the equation Idk.. still got me thinking
Hope that helps.. :)
