Question 84468
You need to get to a equation with only one unknow.

---Step#1:  Start with (X + 4Y - 2Z = -8) - (X + 2Y - Z = -3).
becomes 2Y - Z = -5
becomes Z = 2Y+5

Now you need the X to equal in term of Y
Then substitude X and Z to one of the equations to solve Y.