Giúp mình với :(((((

`1`. Tìm `x`

`a, (x + 13) : 5 = 12`

`x + 13 = 12 xx 5`

`x + 13 = 60`

`x = 60 - 13`

`x = 47`

`b, x . 3 - 2018 : 2 = 23`

`x . 3 - 1009 = 23`

`x . 3 = 23 + 1009`

`x . 3 = 1032`

`x = 1032 : 3`

`x = 344`

`2`. Tính nhanh

`a, 146 + 121 + 54 + 379`

`= (146 + 54) + (121 + 379)`

`= 200 + 500`

`= 700`

`b, 39 . 52 - 48 . 36 + 52 . 61 + 136 . 48`

`= (39 . 52 + 52 . 61) + (136 . 48 - 36 . 48)`

`= [(39 + 61) . 52] + [(136 - 36) . 48]`

`= (100 . 52) + (100 . 48`

`= 100 . 52 + 100 . 48`

`= 100 . (52 + 48)`

`= 100 . 100`

`= 10000`