So n is 2 more than some multiple of 7, so n = 7k+2, for some positive integer k.
2n+1 = 2(7k+2)+1 = 14k+4+1 = 14k+5 When 14k+5 is divided by 7, 2k+0 7)14k+5 14k 5 0 5 So the remainder is 5. Edwin