So I guess we are solving for x here :)
So here is my work...
a=2x+6xz
Basically I think it would be
a=6xz+2x
WAIT WAIT NO I'M WRONG FORGIVE ME!
It's x=a/2(1+3z)
Answer: -8 and -4
This is something you do through trial and error. Making a list or a table like shown below might help.
XYR=36 hope this helps I actually don't know if it is right so I'm so sry if it is wrong so sry