240−[ 13+(23+25.5−x) ]=130
240 - [ 13 + ( 23 + 125 - x ) ] = 130
240 - [ 13 + 148 - x ] = 130
240 - 161 - x = 130
79 - x = 130
x = 130 - 79
x = 51
`240-[13 +(23+25.5-x)] = 130`
`13 +(23+25.5-x)=240 - 130`
`13 +(23+25.5-x)=110`
`23+25.5-x = 110-13`
`23+25.5-x = 97`
`25.5-x = 97-23`
`25.5-x=74`
`125-x=74`
`x=125-74`
`x=51`
Vậy `x=51`