Let $\displaystyle {f{{\left({x}\right)}}}=\frac{{x}}{{{x}+{7}}}.$ Find the values of $\displaystyle {x}$ where $\displaystyle {f}'{\left({x}\right)}={6}$.

Give exact answers (not decimal approximations).


The greater solution is $\displaystyle {x}=$ Preview Question 6 Part 1 of 2  
The lesser solution is $\displaystyle {x}=$ Preview Question 6 Part 2 of 2