The least common denominator of 2/5 and 3/8 is the least common factor of 5 and 8.
Since 8 and 5 have no factors in common, then the least common denominator of 2/5 and 3/8 is:
[tex]8\times5=40.[/tex]Therefore:
[tex]\frac{2}{5}-\frac{3}{8}=\frac{2\times8}{5\times8}-\frac{3\times5}{8\times5}.[/tex]Simplifying the above result we get:
[tex]\frac{2\times8}{5\times8}-\frac{3\times5}{8\times5}=\frac{16}{40}-\frac{15}{40}=\frac{1}{40}.[/tex]Answer:
[tex]\frac{1}{40}.[/tex]