Solution
The electrician can wire 1/12 of a house per hour.
an apprentice can do 1/18 of a house per hour.
=>x/12 + x/18 = 1
[tex]\begin{gathered} \Rightarrow\frac{x}{12}+\frac{x}{18}=1 \\ \\ \Rightarrow\frac{5x}{36}=1 \\ \\ \Rightarrow x=\frac{36}{5}\text{ hours} \end{gathered}[/tex]Therefore, it will take 36/5 hours to wire the house together.
