I + M = 500
M + D = 800
I + D = 700
2 × ( M + I + D) = 500 + 800 + 700
2 × ( M + I + D) = 2000
M + I + D = 2000 : 2
M + I + D= 1000
I + M = 500
D = 1000 - 500
D = 500 castane
M + D = 800
I = 1000 - 800
I = 200 castane
I + D = 700
M = 1000 - 700
M = 300 castane