Question

Replace A, B, by suitable numerals.
$$\begin{gathered} \begin{array}{cc}& A\\ +& A\\ +& A\end{array} \\ \overline{\underline{\begin{array}{cc}B& A\end{array}}} \end{gathered}$$

Answer 1

$A+A+A=A$ (with 1 being carried over)
This is satisfied if $A$ is equal to $5$.

When $A=5$:

$A+A+A=15$ (1 is carried over)

Or $B=1$
∴ $A=5andB=1$