3 7/8 - 1 9/10 =

3 \(\frac{7}{8}\) - 1 \(\frac{9}{10}\) = \(\frac{31}{8}\) - \(\frac{19}{10}\) = \(\frac{310}{80}\) - \(\frac{152}{80}\) = \(\frac{158}{80}\) = \(\frac{79}{40}\) = 1 \(\frac{39}{40}\)