The sign of the product of -21 and 451 is going to be negative. That is because of the rule when you are multiplying a positive number times a negative number. A positive number times a negative number will always be negative. Here are some helpful rules to know:
positive * positive = positive
negative * positive = negative
negative * negative = positive (the negatives cancel each other out)
Since this question has numbers that fit the second case, the answer will be negative.
