A charge of #12 C# is passing through points A and B on a circuit. If the charge's electric potential changes from #36 J# to #18 J#, what is the voltage between points A and B?
Voltage is defined as the electric potential difference between two points per unit charge. So, find the electric potential difference between points
Note that volts is joules per coulomb, so the units here make physical sense (checking that the units make sense is a useful way to troubleshoot maths in physics).