Question

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

x + 5y – z = 6
3x – y – 2z = 4
3x – 2y + 3z = 13

x + 5y + 6

x + 5y – 6

–x – 5y + 6

–x – 5y – 6

Answer 1

the substitution method means that you solve for one of the 3 variables in the first equation in terms of the other two, then you substitute the expression for that variable into the 2nd equation to eliminate one variable, then repeat for the 3rd equation to actually get the answer for one variable.

Your problem doesn't even ask you to do all that... all you have to do is notice that it says you are going to substitute an expression for z into the 2nd and 3rd equations... that means you need to change the first equation into an expression solved for z.

x + 5y - z = 6

Solve for z...

z = ???