Question 1006670
Case-I
{{{x= sqrt(20^2-12^2) + sqrt(13^2-12^2) + 9}}}
=> {{{x = 30}}}

Case-I
{{{x= sqrt(20^2-12^2) - sqrt(13^2-12^2) + 9}}}
=> {{{x = 20}}}

Draw figures to understand clearly