Question 168256
Trial and error sounds good (with a bit of extra thinking on the side)
If the number is twice the sum of its digits then the number must be even. Lets try 12.
12. 1 + 2 = 3 but 12 is not twice 3.
Using that idea the numbers have to total at least 7 so double 7 would be 14.
The two digit number with digits totalling 7 would be 16. 
16. 1 + 6 = 7 but 16 is not twice 7 but we are getting closer (next even number to try is 18)
18. 1 + 8 = 9 and 18 is twice 9
So the number is 18.