5/6-7/12+9/20-11/30+13/42=(1/2+1/3)-(1/3+1/4)+(1/4+1/5)-(1/5+1/6)+(1/6+1/7)=1/2+1/3-1/3-1/4+1/4+1/5-1/5-1/6+1/6+1/7=1/2+1/7=7/14+2/14=9/14
98/70105/70130/70
