The information that is given to us:
x+y+z=7
z=3y
x=y-5
We can now substitute each letter and work it out:
(y-5)+ y +(3y)=7
y+y+3y=7+5
5y=12, then divide each side by 5 and you'll get: Y=2.4
Once you know the value of Y, you substitute Y again:
Z=3(2.4) -> Z=7.2
X=2.4-5-> X= -2.6
Finally, to make sure this is the correct answer, you add up everything and it should be the given answer:
-2.6+2.4+7.2=7
I hope this was useful!
