1/6+8/15+3/28-2/35-7/44 =(1/2 - 1/3) + (1/3+1/5) + (1/4 -1/7) - (1/5 -1/7) - (1/4-1/11) =1/2 - 1/3 + 1/3+1/5 + 1/4 -1/7 - 1/5 +1/7 - 1/4+1/11 =1/2 + 1/11 =13/22