Question 792748
Let the coordinates of the vertices be (x1,y1,z1), (x2,y2,z2) and (x3,y3,z3).


Then use the following equations:
(x1+x2)/2=3
(x2+x3)/2=-1
(x3+x1)/2=0
Etc.


Solve these 9 equations and get the values of 9 unknowns.


Cheers!