3 x ( y/4 +y/28 + y/70+ y/ 130 ) = 60/13

Đáp án:

 `y=5`

Giải thích các bước giải:

 `3×(y/4+y/28+y/70+y/130)=60/13`

`\to y×(3/4+3/28+3/70+3/130)=60/13`

`\to y×(3/1.4+3/4.7+3/7.10+3/10.13)=60/13`

`\to y×(1-1/4+1/4-1/7+1/7-1/10+1/10-1/13)=60/13`

`\to y×(1-1/13)=60/13`

`\to y×12/13=60/13`

`\to y=60/13:12/13`

`\to y=60/13×13/12`

`\to y=60/12`

`\to y=5`

Vậy `y=5`