Question 272464
There is only one positive integer that is exactly twice the sum of its digits. 
What is this two digit number?

Let x be the tens digit and y the ones digit of the number. The number then is
10*x + 1*y

We are given that

10x + y = 2*(x+y)
10x + y = 2x + 2y
8x = y

Since x and y are both single digit integers x must be 1 and y then is 8.

The number is 18.