Question 344299
Originally let the sides be {{{x}}}cm.
{{{(x+6)^2=100}}}
{{{x^2+12x+36=100}}}
{{{x^2+12x-64=0}}}
{{{(x-4)(x+16)=0}}}
Two solutions but only the positive solution makes sense here.
{{{x-4=0}}}
{{{highlight(x=4)}}}cm
Correct. 
Well done!