What is the missing area 11 + = ×16= ×2=209

Lets say x,y,z are the unknown variables,
11+x=y*16=z/2=209

so first solve for z
z/2=209
z=418

y*16=z/2
y=418/32
y=209/16

x+11=y*16
x=209/16*16-11
x=209-11
x=198

missing area is
11+198=209/16=418/2=209

First subtract 10 from both side
y^2+6y-16=0
(y+8)(y-2)=0
-8 and 2