Formula of Distances =
[tex] \sqrt{(x1 - x2)^{2} + (y1 + y2)^{2} } [/tex]
So we know that Point B has the coordinates (5,2), the x-coordinate of Point A is -7 (this equal to (7,?)) and the distances between both is 13. So, right know ,we just replace everything with our data:
(x1,y1)= (5,2)
(x2,y2)=(-7,?)
