1/4+1/2+0,5; 7/15+2,8; 3 17/20-2,7

1/4+1/2+0,5=1/4+1/2+1/2=1/4+1=1 1/4
7/15+2,8=7/15+2 8/10=14/30+2 24/30=2 38/30=3 8/30=3 4/15;
3 17/20-2,7=3 17/20-2 7/10=3 17/20-2 14/20=1 3/20=1,15

1/4+1/2+5/10 = 1/4+ 1/2+1/2 = 1 1/4

7/15 + 2,8 = 7/15 + 2 8/10 =  7/15 + 28/10 = 14/30+84/30 = 98/30 = 3 8/30 = 3 4/15

3 17/20 - 2,7 = 3 17/20 - 2 7/10 = 3 17/20 - 2 14/20 = 1 3/20