<PRE><B>Question 892476</B>
x + y + z
----------- = 80 {to find average, add the numbers and divide by the number of numbers}
3


74 + 78 + z 
------------ = 80 {substituted 74 and 78 for two of the numbers}
3


152 + z 
-------- = 80  {added 74 and 78}
3 


152 + z = 240 {multiplied each side by 3}
z = 88 {subtracted 152 from each side}


88 is the other number
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