Respuesta :

c = -b + 12
2b - 3c = 1 1/2

2b -3(-b+12) = 1 1/2
2b + 3b -36 = 1 1/2
5b = 37 1/2
b = 37.5/5
b = 7.5

c + 7.5 = 12
c = 4.5

b = 7.5   c = 4.5

Hope this helps :)