Final answer:
If 100 electric field lines are leaving a 4 C charge, the same number of field lines would end on a 3 C charge, resulting in 100 field lines.
Step-by-step explanation:
In a system with parallel conducting plates called a parallel plate capacitor, the relationship between the voltage and the stored charge can be observed. Each electric field line starts on a positive charge and ends on a negative charge, with the number of field lines being proportional to the amount of charge. Therefore, if 100 electric field lines are leaving a 4 C charge, then the same number of field lines would end on a 3 C charge, resulting in 100 field lines.