Find the values of the letters in the following and give reasons for the steps involved.
$3A\underset{–}{+25}\underset{–}{B2}$

If $A+5$ must give $2$ as the unit digit of the sum , then $A$ has to be $7$.

$B=3+2+1$ (carry over) $=6$

$A=7$ and $B=6$