Question 874986
By the pythagorean theorem,
{{{x^2+(x+1)^2=(x+2)^2}}}
Multiply
{{{x^2+x^2+2x+1=x^2+4x+4}}}
Subtract x^2+4x+4
{{{x^2-2x-3=0}}}
Quadratic formula:
*[invoke quadratic "x", 1, -2, -3 ]
<h3> Because the sides can't be negative, x=3.</h3>