First, look at the negatives. Remember 'minus a minus is a plus?' That means any pair of - signs cancel each other out. If you have an even number of - signs, then you have pairs that all cancel out and you get a +. If you have an odd number of - signs, then you have a bunch of pairs that cancel out and one - at the end, giving you a - . In this problem the first two - signs cancel out, leaving a - , so the answer has a - in front of it.
- something
Then you just multiply the numbers together.
2 * 5 * 1 * 2 = 20
Answer: -20