Answer
7500 containers are used.
Work Step by Step
The first step is to determine the total number of bolts needed by multiplyng the number of bolts needed for each tower times the number of towers.
$600,000 \times 2 = 1,200,000$
To determine how many containers are needed you must divide the total number of bolts by the number of bolts per container.
$1,200,000 \div 160 = 7500$