You can put this solution on YOUR website! Take you problem and break it down into its parts first.
(x+y) becomes x+y.
-(y+z) becomes -y-z because you need to distrubute the -1 and a negative plus a positive equals a negative.
-(z+x) becomes -z-x because you have to distribute like before.
Now write out what you now have which is x+y-y-z-z-x.
Now cross out the parts that cancel each other out . So x and -x cross each other out and y and -y cancel each other out. Leaving you with -z-z.
Now all you need to do is simplify the like terms giving you -2z
All in all (x+y)-(y+z)-(z+x) can be simplifed to -2z.
I hope this helped you to understand how to do this type of problem in the future. You could also go to www.wolframalpha.com for math help to check your answers.
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