Answer:
The width of the rectangle is 6cm.
Step-by-step explanation:
Perimeter=2(length+width)
28=2(8+w)
Distribute 2 into the parentheses
28=16+2w
Combine like terms
28-16=2w
12=2w
Divide both sides by 2
6=w
I hope this helps! Please comment if you have any questions.