(-6,-3) and (-1,x)=13 find the value of A

Distance between two point can be calculated by the equation:

D=sqrt((x2-x1)^2+(y2-y1)^2)
Then,
13=sqrt((-1-(-6))^2+(x-(-3))^2)
We can square both sides to get rid of the square root,
169=(-5)^2+(x-(-3))^2
169-25=(x-(-3))^2
144 =(x-(-3))^2
By taking the square root in both sides, then
12=x+3
In this case,
X=12-3=9

Ithink is a. true, but not sure