\(8\dfrac{7}{13}.5\dfrac{1}{4}+3\dfrac{14}{17}.5\dfrac{1}{4}\)
\(=\dfrac{111}{13}.\dfrac{21}{4}+\dfrac{65}{17}.\dfrac{21}{4}\)
\(=\dfrac{21}{4}.\left(\dfrac{111}{13}+\dfrac{65}{17}\right)\)
\(=\dfrac{21}{4}.\dfrac{2732}{221}\)
\(=\dfrac{14343}{221}\)