The average age of three people is 25. If two of the people are 22, how old is the third person...?
A.23
B.25
C.28
D.31
E. None correct

D.31

To find the average, we must add all the numbers up and then divide by the amount of numbers there.
Here we have 3 numbers, which two values are given and the average.
So average A, is found by adding all number then dividing by the number of numbers added.
Let's say the average, 25 = 22+22+x/3
Combine like terms, so 25=44+x/3
Then to cancel out the three on the left we must multiply 3 on both sides. 3•25=44+x/3•3
Simplify the equation into
75=44+x
Now we subtract 44 from both sides to move it over to the left, so we can isolate the variable.
75-44=44+x-44
Simplify
31=x

The third person is D. 31