Assuming this is a rectangle (can't be a square since the length and width must be identical)
The Formula for Perimeter is Length*2+Width*2
Solve for W (width)
10*2+W*2=48
20+W*2=48
W*2=48-20
W*2=28
W=28/2
W=14
The Width must be 14.
Hope this helped!
