a) a+b+c=1000.
a-50/100a=1/2a
b-2/3b=1/3b
c-80/100c=1/5c
am si simplificat unde s-a putut.
sumele ramase sunt egale:
1/2a=1/3b=1/5c
si putem scoate b si c in functie de a
b=3a/2
c=5a/2
inlocuim in prima ecuatie
a+3a/2+5a/2=1000 si rezolvam
10a/2=1000
a=200
b=300
c=500
b) a a cheltuit - 50/100*200=100
"b" a cheltuit - 2/3*300=200
"c" a cheltuit - 80/100*500=400
c.) b/a+b+c=300/1000=30%.