1. Les bombetes de llum 2. Bombetes 100W= x+4 3. Bombetes 60W= x 4. 60x+100x+4=2640 5. 60x+100x+400=2640 6. 60x+100x=2640-400 7. 160x=2240 8. X=2240160=14 9. Bombetes 60W=14 10. Bombetes100W=18