(3/4-4/5)*7,8+(2/3+4/7)*7/13=83/300
3/4-4/5=-1/20
-1/20*7,8=-1/20*7 8/10=-1/20*78/10=-39/100
2/3+4/7=26/21
26/21*7/13=2/3
-39/100+2/3=83/300
(3/4-4/5)*7,8+(2/3+4/7)*7/13=83/300
3/4-4/5=-1/20
-1/20*7,8=-1/20*7 8/10=-1/20*78/10=-39/100
2/3+4/7=26/21
26/21*7/13=2/3
-39/100+2/3=83/300