x(y+z)=5y(x+z)=10z(x+y)=13
xy+xz=5
xy+yz=10
xz+yz=13
yz=13-xz
xy+13-xz=10
xy=10-13+xz=xz-3
xz-3+xz=5
2xz=8
xz=4
xy=5-4=1
yz=10-1=9
z=4/x
y*4/x=9
z=9/y
y=1/x
z=9:1/x=9x
9x=4/x
4=9x^2
x^2=4/9
x=2/3
z=4:2/3=4*2/3
z=6
y=1/x=1*3/2
y=1.5=1 1/2
x(y+z)=5
y(x+z)=10
z(x+y)=13
xy+xz=5
xy+yz=10
xz+yz=13
yz=13-xz
xy+13-xz=10
xy=10-13+xz=xz-3
xz-3+xz=5
2xz=8
xz=4
xy=5-4=1
yz=10-1=9
z=4/x
y*4/x=9
z=9/y
y=1/x
z=9:1/x=9x
9x=4/x
4=9x^2
x^2=4/9
x=2/3
z=4:2/3=4*2/3
z=6
y=1/x=1*3/2
y=1.5=1 1/2