a=nr prune
a-3-13= a-16 =prune dupa ce Radu ia 1/5 din rest
a/5 + 4 =Maria
a-a/5-4=(5a-a)/5-4=4a/5-4 = rest
(4a/5-4)x1/5=4a/25-4/5
a/5+4+4a/25-4/5=a-16
5a+100+4a-20=25a-400
16a=480
a=30
Maria 30x1/5+4=10 prune
30-10=20
Radu 20x1/5+3=7 prune
rest in farfurie 30-10-7=13 prune