Factor 2x(a-1)-y(a-1)

$2 x (a - 1) - y (a - 1)$

Factor $a - 1$ out of $2 x (a - 1)$ .

$(a - 1) (2 x) - y (a - 1)$

Factor $a - 1$ out of $- y (a - 1)$ .

$(a - 1) (2 x) + (a - 1) (- y)$

Factor $a - 1$ out of $(a - 1) (2 x) + (a - 1) (- y)$ .

$(a - 1) (2 x - y)$