x.x
10x
2x
20= x.x+12x+20
-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
