Question 1109698
Figure seems to imply a right angle along the segment of x and 3;
If h is the vertical segment from the bottom point to the segment of the x and 3, then  {{{h^2+3^2=5^2}}} and then {{{h=sqrt(25-9)=4}}}.


The triangle on the left is also expected to be a right triangle, if the right-side triangle were a right triangle.  This means  {{{x^2+h^2=8^2}}}, 
and {{{x^2=64-16}}}
{{{x^2=48}}}
{{{x=sqrt(12*4)=sqrt(3*4*4)=highlight(4*sqrt(3))}}}.


You can redo this problem solution using the variable h as assigned to solve for x and get a formula if you wanted.