Giúp em vs em cảm ơn mn nhìu

Bài `3`

`a, [1824 - (526 + 2x)] + 318 = 1420`

`1824 - 526 - 2x + 318 = 1420`

`1616 - 2x = 1420`

`2x = 1616 - 1420`

`2x = 196`

`x = 196 : 2`

`x = 98`

Vậy `x = 98`

`b, 5225 : [215 - (3x - 18)] = 25`

`215 - 3x + 18 = 5225 : 25`

`233 - 3x = 209`

`3x = 233 - 209`

`3x = 24`

`x = 8`

Vậy `x = 8`

Bài `4`

`a, 5.10^4 - 4.10^3 + 6.10^2 - 5.10`

`= 5.10000 - 4.1000 + 6.100 - 5.10`

`= 50000 - 4000 + 600 - 50`

`= 46000 + 550`

`= 46550`

`b, 28.56 - 28.46 + 72.55 - 72.45`

`= 28.(56 - 46) + 72.(55 - 45)`

`= 28 . 10+  72.10`

`= 10.(28 + 72)`

`= 10.100`

`= 1000.`