Question

6分之5减12分之7+20分之9减30分之1+42分之13=? 要过程和答案!

Answer 1

原式=(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
=9/14