ответ: 1

[tex]\displaystyle 2x^2+3x+20=x^2+12x\\2x^2+3x+20-x^2-12x=0\\x^2-9x+20=0\\x^2-4x-5x+20=0\\x(x-4)-5(x-4)=0\\(x-4)(x-5)=0\\x-4=0,x-5=0\\x_1=4,x_2=5[/tex]