(x+6)^2-x^2 = 60/100x^2
x^2 + 12x + 36 - x^2 - 6/10x^2 = 0
-6/10x^2 + 12x + 36 = 0
x^2 - 12*10/6x - 36*10/6 = 0
x^2 - 20x - 60 = 0