Tính hợp lí: (6888 : 56 - 11^2).26 + 13.72 + 13.22

d)(6888:56-11^2).26+13.72+13.22
c)-1/5.4/7+-1/5.10/7+(-2/5)^1
b) 1/1.2+1/2.3+....+1/99.100