(6,6-3_3/14)*5_5/6 / (21-1,25):2,5 = 2,5
1 2 5 3 4
1) 6_3/5 - 3_3/14 = 6_42/70 - 3_15/70 = 3_27/70
2) 5_5/6 * 3_27/70 = 35 / 6 * 237 / 70 = 79/4
3) 21-1,25 = 19,75
4) 19,75 : 2,5 = 79/4 * 10/25 = 790/100 = 7,9
5) 79/4 : 7,9 = 79 / 4 * 10 / 79 = 10/4=5/2 = 2,5