`color{#8FBC8F}{~} color{#C1FFC1}{b} color{#B4EEB4}{u} color{#9BCD9B}{i} color{#698B69}{g} color{#2E8B57}{i} color{#54FF9F}{a} color{#4EEE94}{p} color{#43CD80}{h} color{#98FB98}{o} color{#008B45}{n} color{#00FF00}{g} color{#00EE00}{9} color{#00CD00}{9} color{#ADFF2F}{9} color{#228B22}{~}`

`x/25=-3/15 . 7/6`

`=> x/25 = (-7)/30`

`=> 30x=25.(-7)`

`=> 30x = -175`

`=> x = -175:30`

`=> x = -35/6`

Vậy `x=-35/6`

---------------------

`x+7/5=9/8 . 4/27`

`=> x+7/5=1/6`

`=> x = 1/6-7/5`

`=> x = 5/30-42/30`

`=> x = -37/30`

Vậy `x=-37/30`

---------------------

`x:5/11=-4/12 . 6`

`=> x:5/11=-2`

`=> x=-2 . 5/11`

`=> x=-10/11`

Vậy `x=-10/11`

`*** a/b=c/d=> ad=bc`