Làm ba câu đó thôi nhé cả nhà

`bb{211}`

`11, 5^(2 . x- 3) - 2 . 5^2 = 5^2 .3`

`5^(2 . x - 3) - 2 . 25 = 25 . 3`

`5^(2 . x - 3) - 50  = 75

`5^(2 . x - 3) = 75 + 50`

`5^(2 . x - 3) = 125`

`5^(2x - 3) = 5^3`

`2x - 3 = 3`

`2x = 3 + 3`

`2x = 6`

`x= 3`

``

`12, 

`3^(x + 2) . 2 = 7^2 + 5 . 2008^0`

`3^(x + 2) . 2 = 49 + 5 . 1`

`3^(x + 2) . 2 = 49 + 5`

`3^(x + 2) . 2 = 54`

`3^(x + 2) = 54 : 2`

`3^(x + 2) = 27`

`3^(x + 2) = 3^3`

`x + 2 = 3`

`x= 3 - 2`

`x= 1`

``

`13, 1125 - 10^(x - 3) = 15^2 - 10^2`

`1125 - 10^(x - 3) = 225 - 100`

`1125 - 10^(x -3) = 125`

`10^(x - 3) = 1125 - 125`

`10^(x - 3) = 1000`

`10^(x - 3) = 10^3`

`x-3 = 3`

`x= 3 + 3`

`x= 6`