x2+6x8=3x+7-{x}^{2}+6x-8=3x+7

1
Move all terms to one side.
x26x+8+3x+7=0{x}^{2}-6x+8+3x+7=0

2
Simplify  x26x+8+3x+7{x}^{2}-6x+8+3x+7  to  x23x+15{x}^{2}-3x+15.
x23x+15=0{x}^{2}-3x+15=0

3
Use the Quadratic Formula.
x=3+51ı2,351ı2x=\frac{3+\sqrt{51}\imath }{2},\frac{3-\sqrt{51}\imath }{2}

Done

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