Hola : )
decimos que ;
a = 2b
b = <img src="https://tex.z-dn.net/?f=%20%5Cfrac%7B1%7D%7B3%7Dc%20" />
la ecuacion seria :
a + b + c = 1200
reemplazando :
2b + 1 / 3c + c = 1200
pero tenemos aun dos incognitas, asi que reemplazamos el termino "b"
2(1 / 3c) + 1 / 3c + c = 1200
ahora resolviendo :
<img src="https://tex.z-dn.net/?f=%20%5Cfrac%7B2%7D%7B3%7D%20c%2B%20%5Cfrac%7B1%7D%7B3%7Dc%2B3c%3D1200%20" />
<img src="https://tex.z-dn.net/?f=%20%5Cfrac%7B2c%2B1c%2B3c%7D%7B3%7D%3D1200%20" />
<img src="https://tex.z-dn.net/?f=%20%5Cfrac%7B6c%7D%7B3%7D%20%3D1200" />
<img src="https://tex.z-dn.net/?f=6c%3D1200%2A3" />
<img src="https://tex.z-dn.net/?f=6c%3D3600" />
<img src="https://tex.z-dn.net/?f=c%3D%20%5Cfrac%7B3600%7D%7B6%7D%20" />
<img src="https://tex.z-dn.net/?f=c%3D600" />
ahora reemplazamos para hallar b :
<img src="https://tex.z-dn.net/?f=2b%2B%20%5Cfrac%7B1%7D%7B3%7D%20c%2Bc%3D1200" />
<img src="https://tex.z-dn.net/?f=2b%2B%20%5Cfrac%7B1%7D%7B3%7D%2A600%2B600%3D1200%20" />
[img = 10]
[img = 11]
[img = 12]
[img = 13]
[img = 14]
ahora para hallar a :
[img = 15]
[img = 16]
[img = 17]
[img = 18]
[img = 19]
y eso es todo
R : a cada uno le toco :
a)400
b)200
c)600
Espero te ayude.
: D.