Wind chill is a measure of how cold people feel when exposed to wind outside. A good estimate for wind chill can be found using this calculation:

(wind chill) = (air temperature) - 0.7 $\times$ (wind speed),

where temperature is measured in degrees Fahrenheit (${}^{\circ }$F) and the wind speed is measured in miles per hour (mph). Suppose the wind chill is $5^{\circ }$F and the wind speed is $30$ mph. What is the approximate air temperature?