Question

if 21x is a multiple of 3 find all the values of x

Answer 1

Step-by-step explanation:

Since 24x is a multiple of 3, its sum of digits 6+x is a multiple of 3;

So, 6+x is one of these numbers: 0,3,6,9,13,15,18,….

Since x is a digit, it can only be that 6+x=6 or 9 or 12 or 15.

Therefore, x=0 or 3 or 6 or 9.

Thus, x can have any of four different values