Robert's 5 1/8 + 2 1/3 = 7 1/2 is wrong because if 5+2 = 7, I would have to change the denominator of both fractions so they are both the same. The denominator would have to be 24. That would make the fractions 3/24 and 8/24. If you added them together, it would not be able to simplify to 1/2.
Casey's -4 1/2 + 6 3/4 = 2 1/4 is correct because —4 - 6 = 2. In order to make the fractions have the same denominator, you would have to multiply -1/2 by 2 on both numerator and denominator wich would equal -2/4. Now add -2/4 and 1/4 and you get 1/4. If my explaining is confusing, I'm sorry!☜(ﾟヮﾟ☜)
