Answer 1

$\dfrac{7}{ab} - \dfrac{3a+6}{a} \cdot \dfrac{5}{a+2} = \dfrac{7}{ab} - \dfrac{3(a+2)}{a} \cdot \dfrac{5}{a+2}=\dfrac{7}{ab}-\dfrac{15}{a}=\dfrac{7-15b}{ab}$