Which equation is an identity?

3w + 8 - w = 4w - 2 (w - 4)

8 - (6v + 7) = - 6v - 1

5y + 5 = 5y - 6

6m - 6 = 7m + 9 - m

3w + 8 - w = 4w - 2 (w - 4)

is an identity

3w-w + 8 = 4w - 2w + 8

2w + 8 = 2w + 8

2w - 2w = 8 - 8

0 = 0

zero equal to zero implies that any value of w satisfies the statement 3w + 8 - w = 4w - 2 (w - 4) hence it is an identity.