**Voltage:**
$
E\text{ (voltage)} = I\text{ (current in amps)} \times R\text{ (resistance)}
$
**Current:**
$
I\text{ (current in amps)} = \frac{E\text{ (voltage)}}{R\text{ (resistance)}}
$
**Resistance:**
$
R\text{ (resistance)} = \frac{E\text{ (voltage)}}{I\text{ (current in amps)}}
$