20/11*33/23*69/180=1/1*3/1*3/9=1 

\(\frac{20}{11}\cdot\frac{33}{23}\cdot\frac{69}{180}=\frac{20\cdot33\cdot69}{11\cdot23\cdot180}=\frac{9}{9}=1\)

Để mình ghi lại đề bài:

\(\frac{20}{11}\) x \(\frac{33}{23}\) x \(\frac{69}{180}\)

=\(\frac{20x33x69}{11x23x180}\)(x là nhân nhé)

=\(\frac{20x11x3x23x3}{11x23x20x9}\)

=\(\frac{20x11x3x23x3}{11x23x20x3x3}\)=1

Hướng dẫn giải:

a) 987 x 23 + 987 x 77

= 987 x (23 + 77)

= 987 x 100

= 98700

b) 2928 x 69 – 1928 x 69

= (2928 – 1928) x 69

= 1000 x 69

= 69000

20/11*33/23*69/180=20/11*33/23*23/60

\(\frac{20}{11}\times\frac{33}{23}\times\frac{69}{180}=\frac{20}{11}\times\left(\frac{33}{23}\times\frac{23}{60}\right)\)

=\(\frac{20}{11}\times\frac{759}{1380}=\frac{20}{11}\times\frac{11}{20}=\frac{220}{220}=1\)

 215 x 123 - 125 x 23

= 123 x ( 215 - 125 )

= 123 x 90

= 123 x 9 x 10

= 1230 x 9

= 11070

Cấm ai k

 215 x 123 - 125 x 23

= 215 x 123 - 125 x 123 - 125 x 100

= 123 x ( 215 - 125 ) - 125 x 100

= 123 x 90 - 125 x 100

= 11070 - 12500

= -1430

215 x 123 - 125 x 23

= 215 x 23 - 125 x 23 + 215 x 100

= 23 x ( 215 - 125 ) + 21500

= 23 x 90 + 21500

= 2070 + 21500

= 23570

6705+670x123-670x23

= 670x(123-23)+6705

=670x100+6705

=67000+6705

=73705

2917x85-2817x35

=2917x(85-35)

=2917x50

=145850

\(\frac{20}{11}\)x    \(\frac{33}{23}\)x   \(\frac{69}{180}\)=  1

 ( 675,98 + 888,66 + 111,34 ) x 0,01 = 16,7598