Răspuns :
P=30
P=l+l+L+L
l+l+L+L=30
l=5
5+5+L+L=30
10+2xL=30
2xL=30-10
2xL=20
L=20:2
L=10
P=l+l+L+L
l+l+L+L=30
l=5
5+5+L+L=30
10+2xL=30
2xL=30-10
2xL=20
L=20:2
L=10
2(L+l)=30m
2(L+5m)=30m
2L+2·5m=30m
2L+10m=30m
2L=30m-10m
2L=20m
L=20m:2
L=10m...deci lungimea 10m
2(L+5m)=30m
2L+2·5m=30m
2L+10m=30m
2L=30m-10m
2L=20m
L=20m:2
L=10m...deci lungimea 10m