## Elementary Technical Mathematics

$22.222^oC.$
To change from degrees Fahrenheit to degrees Celsius, we use the formula $$C=\frac{5}{9}(F-32^o)=\frac{5}{9}(72^o-32^o)=\frac{5}{9}\times (40^o)=22.222^o$$ that is, $72^oF=22.222^oC.$