@hrsexton –
So 20% of the cost means 80% is depreciable. If straight line, half of that (40% of total) would be used up by year 5, so the CV would be 60% (20% salvage + 40% depreciable remaining). Straight line would result in a loss if your CV was 60% and sale price 50%. Without running numbers, declining balance would take off much more in the beginning, and SOYD is almost as fast as DDL – so my fast “educated guess” would be Straight Line. Using that logic, I had the answer in about 30 seconds, so it's fast. Remember, exam strategy is about speed, so if you can rule out one as not a dep method then two more as highly likely to be wrong, you have it!