Question

The following system is solved by substitution. Which expression is substituted for z in the second and third equations?

x + 4y + z = –10
3x – 3y + 6z = –21
x + 2y + 2z = –10
Answer
x + 4y – 10
x – 4y – 10
–x – 4y – 10
–x + 4y – 10