\(x^2 - 12x + 36 = 90 \\ \\ x^2 - 12x + 36 - 90 = 0 \ / \ move \ terms \ to \ one \ side \\ \\ x^2 - 12x - 54 = 0 \ / \ simplify \\ \\ x = \frac{12 + 6 \sqrt{10} }{2} , \frac{12 - 6 \sqrt{10} }{2} \ / \ quadratic \ formula \\ \\ x = 3(2 + \sqrt{10} ) \ , \ 3(2 - \sqrt{10} ) \ / \ simplify \\ \\\)
So, your answer to this problem is x = 3(2 + √10) , 3(2 - √10).
