I think it's 20 because the line increasing by 2. If you look at the graph carefully you will see that to go from 8 to 12 you have to pass 10 and then 12 and now if you add 2 to 12 you'll get 14. The question mark is after 4 steps from the 12, so we have to add 2 to 12 4 times and if we do that we'll get