Question

In the following, find the digits represented by the letters:
$3$
$\underset{–}{+B}$
$\underset{–}{7}$

Answer 1

The given problem can be rewritten as $3+B=7$, now, subtract $3$ from both sides as follows:

$(3+B)-3=7-3\Rightarrow 3+B-3=4\Rightarrow B=4$

Hence, the letter $B=4$.