cứu mk với cần gấp

C1:

`(x+1)/15 = 1/3`

`3.(x+1) = 15.1`

`3x+3=15`

`3x=15-3`

`3x=12`

`x=12:3`

`x=4`

Vậy `x=4`

C2:

`(x+1)/15 = 1/3`

`(x+1)/15 = (1.5)/(3.5)`

`(x+1)/15 = 5/15`

`=> x+1=5`

    ` x=5-1`

      `x=4`

Vậy `x=4`