n = 7f + 5
2n = 7(2f) + 10
2n = 7(2f) + 7 + 3
2n = 7(2f + 1) + 3
therefore the remainder is 3
2n = 2(7f +5)
you get this formula , but if they ask us that find 2n when divided on 8 not as the same number 7 . this formula , i think will not help ?what i your opinion ?!
Ikhlas