x=cantitatea de marfa
2/9*x=y-40 (prima zi)
4/15*(y-40)=z-20(a doua zi)
3/5*(z-20)=840( a treia zi)⇒(3z-60)/5=840
3z-60=4200
z=(4200+60)/3
z=1420⇒
⇒4/15(y-40)=1420-20
(4y-160)/15=1400
4y-160=21000
y=(21000+160)/4
y=5290
⇒2/9*x=5290-40
2x=5250*9
x=47250/2
x=23625
daca faci verificarea asa iti va da. sper ca e k