Đáp án:
x =`9/8`
Giải thích các bước giải:
( `1/3` `+ x` ) : ( `x +` `3/4` ) `=` `7/9`
( `1/3` `+ x` ) `=` `7/9` . ( `x +` `3/4` )
`1/3` `+ x =` `7/9` . `x +` `7/9` . `3/4`
`1/3` `+ x =` `7/9` . `x +` `7/12`
`=>` `1/3` `-` `7/12` `=` `7/9` `. x - x`
`=>` `4/12` `-` `7/12` = `7/9` `. x -` `9/9` `. x`
`=>` `(-1)/4` `=` `(-2)/9` `. x`
`=> x =` `(-1)/4` : `(-2)/9`
`=> x =` `(-1)/4` . `(-9)/2`
`=> x =` `9/8`
Vậy `x =` `9/8`