Final answer:
Zack had 400 programs printed.
Step-by-step explanation:
Let's assume that the number of programs Zack had printed is x. The cost of printing each program is $0.54, so the total printing cost would be 0.54x.
The plan was to sell each program for $0.75, and Zack had 100 unsold copies, resulting in a loss of $12. This means that the revenue from the sold programs is 0.75(x-100) and his total revenue is 0.75x.
Based on the given information, we can create the equation 0.75x - 12 = 0.54x. Solving this equation, we find that x = 400.