2 câu trả lời
`25 × b - b = 14040 ÷ 45`
`25 × b - b × 1 = 14040 ÷ 45`
`25 × b - b × 1 = 312`
( 25 - 1 ) × b = 312
`24 × b = 312`
`b = 312 ÷ 24`
`b = 13`
$\text{#Dyn}$
`25 × b - b = 14040 ÷ 45`
`25 × b - b × 1 = 14040 ÷ 45`
`25 × b - b × 1 = 312`
( 25 - 1 ) × b = 312
`24 × b = 312`
`b = 312 ÷ 24`
`b = 13`
$\text{#Dyn}$