Most people let the three numbers be x, x+2, and x+4,
then add them up, set the sum equal to 156, solve the
equation for 'x', then calculate x+2 and x+4.
But I do it like this:
Three numbers have the sum of 156.
If all three were the same number, it would be 156/3 = 52.
Great !
Put 52 on the table three times. Their sum is 156 .
Take 2 away from one of them. It becomes 50.
Give the 2 to a different one. That one becomes 52.
All you did was move a 2 around.
But now you have 50, 52, and 54 on the table. Their sum is still 156.