Pg 314 (326) - Q15
If N is divided by 9, the remainder is 5. Pick a number where this works. So 23/9 would leave a remainder of 5; and they want to know what the remainder of 3N would be if you divide it by 9. Well, multiply 23 by 3 and that gives you 69. Next, you divide that by nine and you get a remainder of C, 6.