A + <img src="https://tex.z-dn.net/?f=%20%5Cfrac%7BB%7D%7B2%7D%20" /> = 1000
A + B = 2000.
(1)
B + <img src="https://tex.z-dn.net/?f=%20%5Cfrac%7BC%7D%7B3%7D%20" /> = 1000
B + C = 3000.
(2)
C + <img src="https://tex.z-dn.net/?f=%20%5Cfrac%7BA%7D%7B4%7D%20" /> = 1000
C + A = 4000.
(3)
A + B = 2000 +
B + C = 3000
C + A = 4000 - - - - - - - - - - -
2A + 2B + 2C = 9000
A + B + C = 4500
A + B = 450 - C - - > A + B = 2000 4500 - C = 2000 2500 = C.
(a)
B + C = 450 - A - - > B + C = 3000 4500 - A = 3000 1500 = A.
(b)
C + A = 450 - B - - > C + A = 4000 4500 - B = 4000 500 = B.
(c)
Listos así de sencillo espero q te ayude.