Question

solve algebraically
x-3y-3z=0
2x+5y-5z=1
-x+5y-6z=-9

Answer 1

one approach
first pick a variable to eliminate
using 2 equations at a time eliminate the same variable you will now have one set of simultaneous equation with 2 variables solve use these values in the expression for the eliminated variable to find that value.
always a good practice to check your solution in the original.

take a minute to try this then I will work with you if you get stuck.
best if you show your work.
If you have any questions please ask.

Answer 2

why did you close the question while I am working on it? do you still need it ?