Chapter 5 - Number Theory and the Real Number System - 5.1 Number Theory: Prime and Composite Numbers - Exercise Set 5.1 - Page 256: 73

d = 2 and d = 6

Using divisibility rules, we know that a number is divisible by 4 if its last two digits make a number that is divisible by 4. In 4|963,23d, we look at 3d with d being unknown. When we substitute each of the numbers, 0 - 9, into 3d for d, we find that only 32 and 36 are divisible by 4. Therefore, d = 2 and d = 6.