Answer:
Usually there are the variables x y z but it doesn't matter what they are.
Explanation:
First choose your first variable to solve. Find x by putting all the numbers and variables to one side.
once you found x substitute the answer for x in all the equations. Next find y and substitute your answer in all the equations again.
Once you have solved 2 variables then you are able to solve z.
If you have questions please feel free to ask in the comments below.