1) 45 10/63 - 44 25/84 = 1 10/63 - 25/84 = 73/63 - 25/84 =
= 4*73/252 - 3*25/252 = 292/252 - 75/252 = 217/252 = 31/36
2) 2 1/3 - 1 1/9 = 7/3 - 10/9 = 21/9 - 10/9 = 11/9
3) 11/9 : 4 = 11/36
4) 11/36 - 3/4 = 11/36 - 27/36 = - 16/36
5) 31/36 : (- 16/36) = - 31/16
6) 4 * (- 31/36) = - 31/4 = - 7 3/4