Question 343468
From the Pythagorean theorem,
{{{A^2+B^2=H^2}}}
{{{x^2+15^2=(x+5)^2}}}
Use the FOIL method to expand the right hand side...
{{{x^2+225=x^2+5x+5x+25}}}
{{{x^2+225=x^2+10x+25}}}
{{{10x+25=225}}}
Take it from there to solve for {{{x}}}