13/21×17+8÷21/17 简便运算,我看过好多了,都不怎么样

=17/21×12+8×17/21
=17/21×（12+8)
=17/21×(21-1)
=17/21×21-17/21×1
=17-17/21
=16+4/21
=16又4/21

13/21×17+8÷21/17
=(13/21)×17+8X(17/21)
=(17/21)X13+8X(17/21)
=(17/21)X(13+8)
=(17/21)X21
=17
或
13/21×17+8÷21/17
=221/21+136/21
=17
或
13/21×17+8÷21/17
[(13+8)*17]/21
=21*17/21
=17

[(13+8)*17]/21=21*17/21=17

13/21×17+8÷21/17
=17/21X13+8X17/21
=(13+8)X17/21
=21X17/21
=17

13/21×17+8÷21/17
=13/21×17+8×17/21
= 13/21×17+17×8/21
=17×（13/21+8/21）
=17×1
=17

13/21*17+8*(17/21)
=((13+8)/21)*17
=17