The perimeter P of a rectangle of length L and width l is [tex]P = 2L + 2l[/tex] Here you know P =108 and l=27. Thus you have the equation [tex]108 = 2L + 2 \times 27 = 2L + 54[/tex] You simplify a bit by moving the 54 on the left side [tex]54 = 2L[/tex] and you find L=27 cm.
