5/28+3/20= 5/28:3/20= 5/28-3/20*5/12=
5/28:3/20=0,00297619047 5/28-3/20*5/12=0,11607142857
5/28+3/20=46/140=23/70 5/28/3/20=100/84=25/21 5/28-3/20*5/12=13/112