Human Resource Machine/Year 8

Strategy
This is the first level along a "left path." Years on the left paths are considered "optional" and are intended to be more challenging. This first one isn't particularly tough, but in order to succeed at the optimization challenges, you must remember one important fact: even when you COPYTO a box on the floor, you still wind up holding the same value in your hands.

Therefore, you can start by grabbing a number from the IN belt, and copying the value to a box. Since you are still holding the value, you just need to add it to itself two more times to triple the value. So you can instruct the worker to add the number you just copied to a box two times, and drop the result on the OUT belt.

a:   INBOX COPYTO  0 ADD     0 ADD     0 OUTBOX JUMP    a

Optimizing
It is not possible to further optimize this solution.