Final answer:
The number 7 lead in a 9-cylinder radial engine magneto distributor is connected to the 7th cylinder.
Step-by-step explanation:
In a 9-cylinder radial engine magneto distributor, the lead for the number 7 cylinder is connected to the 7th spark plug. The cylinder numbering on a radial engine starts from the front and typically goes in a clockwise direction when viewed from the pilot's seat. Therefore, the number 7 lead will go to the 7th cylinder, counting from the front of the engine.