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x+y=90-z
Mean= (6x+90+6y-20+6z-100)/3= [6(x+y+z)+90-120]/3
= 2(x+y+z)-10. (x+y+z=90)
= 2(90)-10=170

Answer: C
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x+y=90-z
x+y+z=90

To calculate Avg,

[6x+90+6y-20+6y-100]/3
[6(x+y+z)+(90-20-100)]/3
(540-30)/3
170

Ans C
Bunuel
If x + y = 90 – z, what is the average (arithmetic mean) of (6x + 90), (6y – 20) and (6z – 100)?

A. 30
B. 90
C. 170
D. 180
E. It cannot be determined from the information given.


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