Find the ordered triple, (p,q,r)
p + 2q = 0
q - 2r = 0
p + r = 8
Hint: in any one of the equations, manipulate it to leave an equation that gives one variable in terms of another. Plug this into a different equation. What do you get?
For example, since p+r=8, we know that p=8-r (subtract r from both sides). Plugging this in to p+2q=0 gives 8-r+2q=0.
Doing this will eventually eliminate the variables so you're left with a simpler system.