kaktolong dijawab no 61 ya yg cepet besok mau kumpul

p:q:r=5x:4x:3x
k=72cm
72cm=5x+4x+3x
72cm=12x
x=72:12
x=6
p=5×6=30
q=4×6=24
r=3×6=18
L=½.a.t=½.18.24=216cm2