หา a ก่อน
$\frac{2}{1+\frac{1}{1+\frac{1}{8}}}$
=$\frac{2}{1+\frac{1}{\frac{9}{8}}}$
=$\frac{2}{1+\frac{8}{9}}$
=$\frac{2}{\frac{17}{9}} $
=$\frac{18}{17} $
หา b
=$\frac{3}{1+\frac{1}{1+\frac{1}{7} } } $
=$\frac{3}{1+\frac{1}{\frac{8}{7} } } $
=$\frac{3}{1+\frac{7}{8} } $
=$\frac{3}{\frac{15}{8} }$
=$\frac{24}{15} $
ab = $\frac{18}{17} \times \frac{24}{15} $
ab = $\frac{144}{85} = 1\frac{59}{85} $
ตอบ $1\frac{59}{85}$ ครับ