Hey there! :D
We know that:
- the perimeter is all the sides added up
- Both pairs of opposite sides have the same length.
Two sides are equal to 4.
4*2= 8
23-8= 15
Since the other side (or both lengths) are equal in length, divide 15 by 2.
15/2= 7.5
The length is equal to 7.5.
I hope this helps!
~kaikers