Cardinal Number set {105, 107, 109, ..., 255}

Question

I understand the equation until the last part.

255 = 105 + 2n - 2

255 = 103 + 2n

253 = 2n

? = n

I know the answer is 76, but I'm not sure how to get there...

Thanks!

Answer 1

255=105+2(n-1)

255=105+2n-2

255=103+2n

255-103=2n

152=2n

n=76