`a, 6` $\vdots$ `n `
`=>n ∈ Ư_((6))={±1;±2;±3;±6}`
Vậy `n ∈ {±1;±2;±3;±6}`
`b, 7` $\vdots$ `n - 2`
`=>n-2 ∈ Ư_((7))={±1;±7}`
`=>n ∈ {3;1;9;-5}`
Vậy `n ∈ {3;1;9;-5}`
`c, n+5` $\vdots$ `n -2`
`<=>n-2+7` $\vdots$ `n - 2`
`<=>7` $\vdots$ `n - 2`
`=>n-2 ∈ Ư_((7))={±1;±7}`
`=>n ∈ {3;1;9;-5}`
Vậy `n ∈ {3;1;9;-5}`