Упростите выражения 12/13×13/12×14/15×15/14×16/17×17/16×18/19×19/18×20/21

Question

Упростите выражения 12/13×13/12×14/15×15/14×16/17×17/16×18/19×19/18×20/21

Answer 1

(12/13*13/12)*(14/15*15/14)*(16/17*17/16)*(18/19*19/18)*20/21=1*1*1*1*20/21=20/21.