Question 755916
You can identify the center for C1, being at (-2,-4).
You know something about the center for C2, that it is (h,1).
You are given that the distance between those centers is 13 units. 


Use the distance formula and solve for h.  Forming the equation for this distance starts us with :
{{{sqrt((-2-h)^2+(1-(-4))^2)=13}}}
Solve for h.