\(\dfrac{-21}{8}+\dfrac{17}{14}=\dfrac{-147}{56}+\dfrac{68}{56}=\dfrac{-147+68}{56}=\dfrac{-79}{56}\)
\(\dfrac{-21}{8}+\dfrac{17}{14}=\dfrac{-294}{112}+\dfrac{136}{112}=\dfrac{-158}{112}=\dfrac{-79}{56}\)
\(\dfrac{-21}{8}+\dfrac{17}{14}=\dfrac{-147}{56}+\dfrac{68}{56}\\=\dfrac{\left(-147\right)+68}{56}=\dfrac{-79}{56}\)
\(\dfrac{-21}{8}+\dfrac{17}{14}\)
\(=\dfrac{-147}{56}+\dfrac{68}{56}\)
\(=\dfrac{-79}{56}\)