Question

1减2分之三加6分之5减12分之七.减90分之19加110分之21

Answer 1

=1-(2+1)/1×2+(2+3)/2×3-(3+4)/3×4+……-(9+10)/9×10+(10+11)/10×11

=1-1/1-1/2+1/2+1/3-1/3-1/4+1/4-1/9-1/10+1/10+1/11

=1/11