We know Dave has a board that is 3 1/4 long:
and we need to subtract 1 and 7/8 to the board. So, we have
where, we eliminated 1 and 7/8, denoted in purple color. Then, it remains 1 and 3/8, denoted in green color.
Therefore, we have obtained:
[tex]3\frac{1}{4}-1\frac{7}{8}=1\frac{3}{8}[/tex]
Therefore, the answer is:
[tex]1\frac{3}{8}[/tex]
which corresponds to option B
