Draw a line parallel to the line joining the centers of the circles from A which will meet the line joining B and the center of the rightmost circle at C . Obviously , the angle ACB will be a right angle , with AC = r1 + r2 = 25 and BC = r2 - r1 = 7 . Hence , AB = √AC2 + BC2 = √674
Edit - The small mistake -----Angle ABC is actually 90 degree .