tolong bantu ngerjain soalnya nya pake cara

Keliling persegi panjang = 84 cm 
p - l = 6  ⇒p = 6 + l
K = 2 ( p + l )
84 = 2 ( 6 + l + l ) 
84 = 12 + 4l
4l = 84 - 12 
l = 72/4 = 18
p = 6 + l = 6 + 18 = 24 
p = 24 cm dan l = 18 cm
semoga membantu