let's firstly convert the mixed fractions to improper fractions, and then subtract.
[tex]\bf \stackrel{mixed}{2\frac{3}{5}}\implies \cfrac{2\cdot 5+3}{5}\implies \stackrel{improper}{\cfrac{13}{5}}~\hfill \stackrel{mixed}{1\frac{3}{8}}\implies \cfrac{1\cdot 8+3}{8}\implies \stackrel{improper}{\cfrac{11}{8}} \\\\[-0.35em] \rule{34em}{0.25pt}\\\\ \cfrac{13}{5}-\cfrac{11}{8}\implies \stackrel{\textit{using the LCD of 40}}{\cfrac{(8)13~~-~~(5)11}{40}}\implies \cfrac{104-55}{40}\implies \cfrac{49}{40}\implies 1\frac{9}{40}[/tex]
