`45 xx ( 32 + 17 ) + 55 xx ( 32 + 47 )`
`=(32+47)xx(45+55)`
`=100xx79`
`=7900`
`( 125 xx 7 ) : 25`
`=(25xx5xx7):25`
`=(5xx7)xx(25:25)`
`=35:1`
`=35`
`64 xx 19 + 17 xx 19 xx 2`
`=19xx(64+17xx2)`
`=19xx(64+34)`
`=19xx98`
`=1862`
`( 3000 + 150 ) :75`
`(75.40+75.2):75`
`=[75(40+2)]:75`
`=(40+2)xx(75:75)`
`=42:1`
`=42`
`15 xx x - x = 280`
`=>15x-x=280`
`=>14x=280`
`=>x=20`
Vậy `x=20`
`7 xx x = 360 + x`
`=>7x=360+x`
`=>7x-x=360`
`=>6x=360`
`=>x=60`
Vậy `x=60`