Answer:
20 ft=w
Explanation:
If you have 100 ft of fencing, that is the perimeter.
Let w = the width of the dog pen
w+10 = the length of the dog pen (based on the conditions given)
Perimeter = width + width + length + length
100 = w+w+w+10+w+10
100=4w+20 subtract 20 from both sides
80=4w Divide both sides by 4
20 ft=w
im sorry if this is not right