Whar number must be added to both sides of the equation to solve it by completeing the square? 3x^2+15x=9

Question

(1)225
(2)25
(3)6.25
(4)5

Answer 1

first divide all terms by 3 to get
x^2 + 5x = 3
x^2 + 5x + 25/4 = 3 + 25/4

and I know 25/4 = 6/25

Answer 2

clearly I meant to type
nd I know 25/4 = 6.25