P=2w+(2w-3)
60=4w-3
63=4w
15.75=w
l=2w-3
l=(2×15.75)-3
l=31.5-3
l=28.5
This answer doesn't add up so if you meant the COMBINED width then:
P=w+(2w-3)
60=3w-3
63=3w
21=w
l=2(21)-3
l=42-3
l=39
(This answer checks out so this is probably what you meant hope I helped)