a) {x,y,z} d.p. {3,4,7}
x/3=y/4=z/7=k
x/3=k => x=3k => x= 3ori4=12
y/4=k => y=4k => y=4ori4=16
z/7=k => z=7k => z=7ori4=28
z+x=40
7k+3k=40
10k=40
k=40/10
k=4
b) {x,y,z} d.p. {2,3,6}
x/2=y/3=z/6=k
x/2=k => x=2k => x=2ori6=12
y/3=k => y=3k => y=3ori6=18
z/6=k => z=6k => z=6ori4=24
z-x=24
6k-2k=24
4k=24
k=6