Answer
2,743 deliveries
Work Step by Step
$C(x) = 80\sqrt[3] x +500$
$1620 = 80\sqrt[3] x +500$
$1120 = 80\sqrt[3] x$
$1120/80 = 80\sqrt[3] x/80$
$14 = \sqrt[3] x$
$14^3 = (\sqrt[3] x)^3$
$2744 = x$
$2744-1=2743$
One delivery was deducted since we need to keep costs below 1620 dollars.