Answer:
12
Explanation:
(x-1)+(y+1)+(z-1)
= x -1 + y + 1 + z - 1
= x + y + z -1
= (x + y + z) -1
given that x+y+z = 13, substitute this value into the equation aove
(x + y + z) -1
= 13 - 1
= 12
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