MAth help?

Question

IF the sides of a square are increased by 3 in., the area becomes 64 in squared. Find the length of a side of the original square.

I have to solve if by factoring
the obvioius answer is 5, but i need to use factoring.
this is what i got so far.

X+3 squared - 64
X2 +6x +9 =64
(X-5) (X+11)
now how do i get that back to my answer
thanks

Answer 1

(X-5) (X+11) = 0 if x=5 or x=-11 but x=-11 is not a reasonable answer because length can not be negative so the correct answer is 5

Note: you could also use the fact that 8 squared=64 so x+3=8