Factor (m+n)(a-2)+(m-n)(a-2)

$(m + n) (a - 2) + (m - n) (a - 2)$

Factor $a - 2$ out of $(m + n) (a - 2) + (m - n) (a - 2)$ .

Factor $a - 2$ out of $(m + n) (a - 2)$ .

$(a - 2) (m + n) + (m - n) (a - 2)$

Factor $a - 2$ out of $(m - n) (a - 2)$ .

$(a - 2) (m + n) + (a - 2) (m - n)$

Factor $a - 2$ out of $(a - 2) (m + n) + (a - 2) (m - n)$ .

$(a - 2) (m + n + m - n)$

Add $m$ and $m$ .

$(a - 2) (2 m + n - n)$

Subtract $n$ from $n$ .

$(a - 2) (2 m + 0)$

Factor.

Add $2 m$ and $0$ .

$(a - 2) (2 m)$

Remove unnecessary parentheses.

$(a - 2) \cdot 2 m$