Answer:
16.5cm
Step-by-step explanation:
[tex]perimeter = 2(l + w)\\l = 3 + w\\perimeter = 60\\2(l + w) = 60\\sub (l = 3 + w) for - l\\2((3+w) + w) = 60\\2(3 + w + w) = 60\\2(3 + 2w) = 60\\6 + 4w = 60\\4w = 60 - 6\\4w = 54\\w = \frac{54}{4}\\w = 13.5\\\\substitute- w= 13- into 2(l = 3 + w)\\l = 13.5 + 3\\l = 16.5[/tex]