Question 973605
<pre>
{{{A^2+16^2}}}{{{""=""}}}{{{20^2}}}

I won't do that same one.  I'll do one exactly like it instead:

{{{X^2+36^2}}}{{{""=""}}}{{{39^2}}}

{{{X^2+1296}}}{{{""=""}}}{{{1521}}}

Subtract 1296 from both sides:

{{{X^2}}}{{{""=""}}}{{{225}}}

{{{sqrt(X^2)}}}{{{""=""}}}{{{"" +- sqrt(225)}}}

{{{X}}}{{{""=""}}}{{{"" +- 15}}}

Two solutions:  X = 15 and X = -15.

Now use the above as a guide to solve your equation.

Edwin</pre>