3 – (-1/2) + 7/4 = ??????

3 – (-1/2) + 7/4 = 3 +1/2 + 7/4
                        = 3 + 2/4 + 7/4
                        = 3 + 9/4
                        = 3 + 2 1/4
                        = 5 1/4

3 + ½ + 7/4 = 14/4 + 7/4 = 21/4