Question 907342
I'm assuming you have values or expressions for a,b, and c. 
You would substitute and solve until you had the left side equaling the right side. 
Example: {{{a=3}}},{{{b=4}}},{{{c=5}}}
{{{a^2+b^2=c^2}}}
{{{3^2+4^2=5^2}}}
{{{9+16=25}}}
{{{25=25}}}
True.
.
.
.
Example: {{{a=5x}}}, {{{b=12x}}}, {{{c=13x}}}
{{{a^2+b^2=c^2}}}
{{{(5x)^2+(12x)^2=(13x)^2}}}
{{{25x^2+144x^2=169x^2}}}
{{{169x^2=169x^2}}}
True.