Đáp án+Giải thích các bước giải:

 `a) 2146 + 1285 + 345 + 215`

`=( 2145+1)+ 1285 + 345 + 215`

`= ( 2145 + 345 ) + ( 1285 + 215 ) + 1`

`= 2490 + 1500+1`

`= 3991`

`1278 + 2356 + 1044 + 1022`

`= (1278+1022) + ( 2356+1044)`

`= 2300 + 3400`

`= 5700`

`b) 234 x 67 + 234 x 23 + 10 x 234`

`=234 x ( 67+23+10)`

`= 234 x 100`

`= 23400`

`564 x 59 - 564 x 19 - 564 x 30`

`= 564 x ( 59-19-30)`

`= 564 x 10`

`= 5640`

Bài 3 

`a) 6 x ( x + 9845 ) = 29042 x 6`

`6 x ( x + 9845 ) = 174252`

`x + 9845 = 174252 : 6`

`x + 9845 = 29042`

`x = 29042 - 9845`

`x = 19197`

`b) ( x : 3 ) x 8 = 8 x 3198`

`x : 3 x 8 = 25584`

`x : 3 = 25584 : 8`

`x : 3 = 3198`

`x = 3198 x 3`

`x = 9594`

$@chienbinhkieuhanh$

`2)`

`a) 2146 + 1285 + 345 + 215`

`= ( 2146 + 345) + ( 1285 + 215)`

`= 2491 + 1500`

`= 3991`

`1278 + 2356 + 1044 + 1022`

`= ( 1278 + 1022) + ( 2356 + 1044)`

`=  2300 +  3400`

`=  5700`

``

`b) 234 xx 67 + 234 xx 23 + 10 xx 234`

`= 234 xx ( 67 + 23 + 10)`

`= 234 xx 100`

`= 23400`

``

`564 xx 59 - 564 xx 19 - 564 xx 30`

`= 564 xx ( 59 - 19 - 30)`

`= 564 xx 10`

`= 5640`

bài `3`

`a) 6 xx ( x + 9845) = 29042 xx 6`

`(x + 9845) = ( 29045) xx 6) : 6`

`x + 9845 = 29042`

`x = 29042 - 9845`

`x =  19 197`

``

`b) ( x : 3) xx 8 = 8 xx 3198`

`( x : 3) = ( 8 xx 3198) : 8`

`x : 3 = 3198`

`x = 3198 xx 3`

`x  = 9594`