5x3+2x3=5x3+5x2x3=75
6x4+3x4=6x4+6x3x4=144
5x4+4x4=5x4+5x4x4=160
7x2+8x2=7x2+7x8x2=140
6 3/7 - 4,135 + 1,235 - 2 9/14 = 57/70
- 4,135 + 1,235 = - 2,9
6 3/7 - 2 9/14 = 6 6/14 - 2 9/14 = 5 20/14 - 2 9/14 = 3 11/14
3 11/14 - 2,9 = 3 11/14 - 2 9/10 = 3 55 /70 - 2 63/70 = 2 120/70 - 2 63/70 = 57/70