Respuesta :

x.x

10x

2x

20= x.x+12x+20

x.x

-4x

-5x

20=x.x-9x+20

(x.x+12x+20)-(x.x-9x+20)

x.x+12x+20-x.x+9x-20

x.x-x.x=0

12x+9x=21x

20-20=0

Answer:21x