Đáp án:
`A.x=2600`
`B.x=107`
Giải thích các bước giải:
`A.(2600+6400)-3x=12.100`
`⇔9000-3x=1200`
`⇔-3x=1200-9000`
`⇔-3x=-7800`
`⇔x=-7800:-3`
`⇔x=2600`
`B.[(6x-72):2-84].28=5628`
`⇔(6x-72):2-84=5628:28`
`⇔(6x-72):2-84=201`
`⇔(6x-72):2=201+84`
`⇔(6x-72):2=285`
`⇔6x-72=285.2`
`⇔6x-72=570`
`⇔6x=642`
`⇔x=107`