[tex] \dfrac{7}{9} \cdot\left(\dfrac{117}{4} - \dfrac{9}{4} \right) = \\ \\ = \dfrac{7}{9} \cdot \dfrac{117-9}{4} = \\ \\ = \dfrac{7}{9} \cdot \dfrac{108}{4} = \\ \\ = \dfrac{7}{9} \cdot 27 = \\ \\ = 7 \cdot \dfrac{27}{9} = \\ \\ = 7 \cdot 3 = \\ \\ = 21 [/tex]
