`@` `\text {Ans}`
`\downarrow`
`[124 - (20 - 4x)] \div 30 = 40`
`\Rightarrow 124 - (20 - 4x) = 40 \times 30`
`\Rightarrow 124 - (20 - 4x) = 120`
`\Rightarrow 20- 4x = 124 - 120`
`\Rightarrow 20 - 4x = 4`
`\Rightarrow 4x= 20 -4`
`\Rightarrow 4x = 16`
`\Rightarrow x = 16 \div 4`
`\Rightarrow x = 4`
Vậy, `x = 4.`
[124-(20-4.x)]:30=40
=>124-(20-4x)=40*30
=>124-(20-4x)=120
=>20-4x=124-120
=>20-4x=4
=>4x-20-4
=>4x=16
=>x=16:4
=>x=4
[124-(20-4.x)]:30=40
=>124-(20-4x)=40*30
=>124-(20-4x)=120
=>20-4x=124-120
=>20-4x=4
=>4x-20-4
=>4x=16
=>x=16:4
=>x=4
