By the product rule,
[tex](fg)'=f'g+fg'[/tex]
so that
[tex](fg)'(7)=f'(7)g(7)+f(7)g'(7)=10\cdot(-1)+4\cdot8=22[/tex]
By the quotient rule,
[tex]\left(\dfrac fg\right)'=\dfrac{f'g-fg'}{g^2}[/tex]
so that
[tex]\left(\dfrac fg\right)'(7)=\dfrac{f'(7)g(7)-f(7)g'(7)}{g(7)^2}=\dfrac{10\cdot(-1)-4\cdot8}{(-1)^2}=-42[/tex]
