Notez suma cu S
I. a cheltuit 4S/9
II. a cheltuit 30/100 din rest
restul =
S-4S/9=5S/9
a cheltuit 30/100*5S/9+50=S/6+50
III . restul este 5S/9-(S/6+50)=7S/18-50
a cheltuit 40/100 din rest +60 adica
40/100*(7S/18-50)+60=7*S/45+40
iV. 750
Acum adun tot ce a cheltuit si egalez cu suma S
S=4S/9+(S/6 +50)+(7S/45+40)+750
aduc la acelasi numitor care e 90
90S=40S+15S+14S+840*90
90 S=69S+840*90
adica 21S=840*90
S=3600 de lei