Question

giúp tớ với 

Answer 1

`42xx15+57xx15+15`

`=15xx(42+57+1)`

`=15xx100=1500`

Answer 2

` 42 xx 15 + 57 xx 15 + 15`

` = ( 42 + 57 + 1) xx 15`

` = 100 xx 15`

`= 1500`

Answer 3

=(42+57+1).15

=100.15

=1500

Answer 4