a) TH1 : (4 + $\frac{1}{5}$) . $\frac{19}{8}$ + (2 + $\frac{5}{8}$) . $\frac{21}{5}$
= 4$\frac{1}{5}$ . $\frac{19}{8}$ + 2$\frac{5}{8}$ . $\frac{21}{5}$
= $\frac{21}{5}$ . $\frac{19}{8}$ + $\frac{21}{8}$ . $\frac{21}{5}$
= $\frac{21}{5}$ . ($\frac{19}{8}$ + $\frac{21}{8}$)
= $\frac{21}{5}$ . $\frac{15}{4}$
= $\frac{63}{4}$
TH2 :
(4 + $\frac{1}{5}$) . $\frac{19}{8}$ - (2 + $\frac{5}{8}$) . $\frac{21}{5}$
= 4$\frac{1}{5}$ . $\frac{19}{8}$ - 2$\frac{5}{8}$ . $\frac{21}{5}$
= $\frac{21}{5}$ . $\frac{19}{8}$ - $\frac{21}{8}$ . $\frac{21}{5}$
= $\frac{21}{5}$ . ($\frac{19}{8}$ - $\frac{21}{8}$)
= $\frac{21}{5}$ . $\frac{-1}{4}$
= $\frac{-21}{20}$
b) $\frac{25}{2}$ . (3 + $\frac{2}{7}$) - $\frac{23}{7}$ . (5 + $\frac{1}{2}$)
= $\frac{25}{2}$ . $\frac{23}{7}$ - $\frac{23}{7}$ . $\frac{11}{2}$
= $\frac{23}{7}$ . ($\frac{25}{2}$ - $\frac{11}{2}$)
= $\frac{23}{7}$ . 7
= 23.
