Question 702398
(x+3)^2 = x^2 + 69


x^2 + 6x + 9 = x^2 + 69


x^2 + 6x + 9 - x^2 = x^2 + 69 - x^2


6x + 9 = 69


6x = 69 - 9


6x = 60


x = 60/6


x = 10


The initial square had a side length of 10 yards.