If the store was ordering a shipment of balls proportional to the 30 45 75 stated above, then the store would have ordered a package with 400 yellow balls, 600 blue balls (heh), and 1,000 pink balls.
Work: There were 150 balls total 30+45+75 =150. 30/150 = x/2000; 45/150 = x/2000; 75/150 = x/2000