Explanation
The four squares at the end have sides that measure 6 inches each. With the boxes stacked as shown, the distance across the bottom of the stack is 6 6, or 12, inches (1 foot). If you go all the way around the stack, the distance in feet is 1 1 1 1, or 4, feet. For one loop around, Julio needs 4 feet of tape. For two loops, he needs twice that, or 8 feet