Answer: B) 6
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Explanation:
Add the equations by adding the terms straight down.
The x terms add to x+x = 2x.
The y terms add to y+(-y) = y-y = 0y = 0, so the y terms go away
The constants add to 5+7 = 12
The z terms add to -z+z = 0z = 0 and those go away as well
After all that adding, we have 2x = 12 which solves to x = 6 after dividing both sides by 2.
