3. When the positive integer $x$ is divided by 6 , the remainder is 3 . What is the remainder when $3 x$ is divided by 6 ?
A 4
B 3
С 2
D 1
E 0
3. B The number $x$ is 3 more than a multiple of 6 , so $x=6 k+3$ for some nonnegative integer value of $k$. And then
$3 x=3(6 k+3)=18 k+9=6(3 k+1)+3$. Hence $3 x$ is 3 more than a multiple of 6 , so leaves remainder 3 when divided by 6 .