Find all possible values of $y$ for which the number $53y1$ is divisible by$3.$ Also, find each such number.

Find the value of $x$ for which the number $x806$ is divisible by $9$. Also, find the number.

Find the value of $z$ for which the number $471z8$ is divisible by $9$. Also, find the number.

Give five examples of numbers, each one of which is divisible by $3$ but not divisible by $9$.

Give five examples of numbers, each one of which is divisible by $4$ but not divisible by $8$.

Replace $A, B \mathrm{and} C$ by suitable numerals.

$5\mathrm{A}+87CB3$

Replace $A, B \mathrm{and} C$ by suitable numerals.

$4\mathrm{C}\mathrm{B}6+369\mathrm{A}8173$

Replace $A, B$ by suitable numerals.

$\begin{array}{cc}& A\\ +& A\\ +& A\\ B& A\end{array}$

Replace $A, B$ by suitable numerals.

$\begin{array}{ccc}& 6& A\\ -& A& B\\ & 3& 7\end{array}$