We have another made up function here, but this is one of those overlay problems. We want the values between 80-110 minus the values between 81-109. Well, the values between 80-110 would be (81+82....+108+109); the values between 81-109 would be (82+83...+107+108). So, if we subtract this second value, there is going to be a great common area of overlap and when you subtract it out the values between 82-108 are all common to both problems and all of these would cancel out. So, the numbers you'd be left with our 81 and 109. Therefore, you'd be left with a total of 190.