Question

if the average (arithmetic mean) of two, seven, and X is 12, what is the value of X?

Answer 1

The average is always the sum of values divided by the number of values.

(2+7+x)/3=12

Multiply both sides by 3
2+7+x=36

Combine like terms
9+x=36

Subtract 9 from both sides
x=27

Final answer: x=27