Question

简便运算：3分之2减6分之5加12分之7减20分之9加30分之11减42分之13=?

Answer 1

2/3-5/6+7/12-9/20+11/30-13/42

=2/3-(1/2+1/3)+(1/3+1/4)-(1/4+1/5)+(1/5+1/6)-(1/6+1/7)

=2/3-1/2-1/3+1/3+1/4-1/4-1/5+1/5+1/6-1/6-1/7

=2/3-1/2-1/7

=1/42