Note the minus signs in the brackets, but come back to them later. Multiply the numbers in the first group of brackets: 48. Now multiply the numbers in the second set: 18. We had one minus sign in the first group, so we need to make the first number negative: -48. And there is a minus sign in the second group: -18. The minus sign between the groups negates the minus sign in the second group changing subtract to add. The sum becomes: -48 + 18. This is like saying what is 18 degrees warmer than 48 degrees below zero? The answer is 30 degrees below zero, or -30. That's your answer!