Question 270519
That depends on what you are given about the right triangle.
You didn't tell us that information, so we can't help you 
until you do.  Are you given the vertices as points?  Are
you given the lengths of two legs?  A leg and the hypotenuse?
A leg and an acute angle?  The hypotenuse and an acute angle?
Let us know what you are given about the right triangle and
then we can tell you how to find the circumcenter algebraically.