[tex]x(x + 7) = 2x(x - 3) \\ x \times x + 7 \times x = 2x \times x - 2x \times 3 \\ {x}^{2} + 7x = 2 {x}^{2} - 6x \: \: | - 2 {x}^{2} \\ - {x}^{2} + 7x = - 6x \: \: | \div x \\ - x + 7 = - 6 \: \: | - 7 \\ - x = - 13 \: \: \times ( - 1) \\ x = 13[/tex]
