The circumcenter is where the perpendicular bisectors meet.
if you sketch the triangle, you will see that it is a right triangle, with the right angle vertex at (2,1)
one perpendicular bisector is x=1, another perpendicular bisector is y=3
they meet at (1,3)
so (1,3) is the answer.
Answer:
1=1 times 2/2 1 + 2=2 times 3/2 1 +2+3=3 times 4/2 1+2+3+4=4 times 5/2 1+2+3+4+5=5 times 6/2
6, 12, 18, 24.
8, 16, 24.
24 is your answer. Hoped I helped!