\(\begin{array}{l} \,\,\,\,\,\,\left( {3 - x} \right).\left( {x - 4} \right).\left( {6 - x} \right) + {x^2}(13 - x) = 0\\ \left( {3x - 12 - {x^2} + 4x} \right)\left( {6 - x} \right) + 13{x^2} - {x^3} = 0\\ \left( { - {x^2} + 7x - 12} \right)\left( {6 - x} \right) + 13{x^2} - {x^3} = 0\\ - 6{x^2} + {x^3} + 42x - 7{x^2} - 72 + 12x + 13{x^2} - {x^3} = 0\\ \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,54x - 72 = 0\\ \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,x = \frac{{72}}{{54}}\\ \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,x = \frac{4}{3} \end{array}\)
