100 x 9 + 100 x 91 x 30 - 21
= 100 x ( 9 + 91 x 30 ) - 21
= 273900 - 21
= 273879
100 x 9 + 100 x 91 x 30 - 21
= 100 x ( 9 + 91 ) x 30 - 21
= 100 x 100 x 30 - 21
= 10 000 x 30 - 21
= 300 000 - 21
= 299 979
_Học _ tốt_
\(100\times9+100\times91\times30-21\)
\(=900+9100\times30-21\)
\(=900+273000-21\)
\(=900+272979\)
\(=273879\)
hok tốt ~~
100×9+100×91×30−21
=900+9100×30−21
=900+273000−21
=900+272979
=273879