Answer: 28
Step-by-step explanation:
The mean of 15 numbers = 12
Then , the sum of the numbers = 12x15 = 180
Let the extra number included be
, then
The new sum = 
And the new total number will increase from 15 to 16
new mean = 13 , so we have :





therefore , the extra number is 28
3x(1.05) = 3.15x
1.05x + 1.05x + 1.05x = 3.15x
Answer: x+3y−9
Step-by-step explanation:
Simplify the expression.
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