Question 378503
YOU ARE DOING GREEEEAT!!!!!!!
Down toward the end you have:
-3(5x+2y=17)...-15x-6y=-57
---and you made a simple error.  It should be.....-15x-6y=-51  (not 57)
Now lets see how this changes the outcome
Instead of --  -21x=-69 you have -21x=-63
and x=3

Now the next step is to substitute x=3 into either of the equations with two unknowns and solve for y.  Then the next step would be to substitute the value you got for y plus the value you have for x (3) into either of the equations with 3 unknowns and then solve for z.

You are doing good---keep it up.

Hope this helps ---ptaylor