3/25 + 0,34 - 4/25 = 0,22
1) 3/25 + 0,34 = 3/25 + 34/100 = 4/100 + 34/100 = 38/100
2) 38/100 - 4/25 = 38/100 - 16/25 = 22/100 = 0,22
7/9 - 0,4 - 4/15 = 1/9
1) 7/9 - 0,4 = 7/9 - 4/10 = 70/90 - 36/90 = 34/90
2) 34/90 - 4/15 = 34/90 - 24/90 = 10/90 = 1/9