$$(x+7)(x-5) = (x+13)x$$

$$ \begin{aligned} (x+7)(x-5) &= (x+13)x&& \text{simplify left and right hand side} \\[1 em]x^2-5x+7x-35 &= x^2+13x&& \\[1 em]x^2+2x-35 &= x^2+13x&& \text{move all terms to the left hand side } \\[1 em]x^2+2x-35-x^2-13x &= 0&& \text{simplify left side} \\[1 em]x^2+2x-35-x^2-13x &= 0&& \\[1 em]-11x-35 &= 0&& \text{ move the constants to the right } \\[1 em]-11x &= 35&& \text{ divide both sides by $ -11 $ } \\[1 em]x &= -\frac{35}{11}&& \\[1 em] \end{aligned} $$

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