1) 5/9 * 2 4/7 = 5/9 * 18/7 = 10/7
2) 4 2/3 - 10/7 = 14/3 - 10/7 = 98/21 - 30/21 = 68/21
3) 2 1/7 + 1 2/3 = 15/7 + 5/3 = 45/21 + 35/21 = 80/21
4) 80/21 / 5= 80/21 * 1/5 = 16/21
5) 68/21 / 16/21 = 68/21 * 21/16 = 4,25
6) 0,8*1,25 = 1
7) 4,25 + 1 = 5,25