Look at your intermediate steps, and ask "Does this look like the right answer?" at each point. Nobody's memory is perfect - so it becomes a question of "How c

Look at your intermediate steps, and ask "Does this look like the right answer?" at each point. Nobody's memory is perfect - so it becomes a question of "How can I tell if I'm going down the right route, and how can I test to spot the mistakes I know I'm going to make?"