Solution:
Given:
[tex]\begin{gathered} Violet=3hrs \\ Fran=5hrs \end{gathered}[/tex]The rates each use to paint one room (living room) is given by;
[tex]\begin{gathered} Violet=\frac{1}{3}room\text{ per hour} \\ Fran=\frac{1}{5}room\text{ per hour} \end{gathered}[/tex]If both work together, their combined rates will be;
[tex]\begin{gathered} \frac{1}{3}+\frac{1}{5}=\frac{5+3}{15} \\ =\frac{8}{15}room\text{ per hour} \end{gathered}[/tex]Hence, the time it will take them to finish painting the room working together is;
[tex]\begin{gathered} \frac{1}{\frac{8}{15}}=1\times\frac{15}{8} \\ =\frac{15}{8}hours\text{ per room} \\ =1\frac{7}{8}hours \end{gathered}[/tex]Therefore, the time it will take them to finish painting the room working together is;
[tex]1\frac{7}{8}\text{ }hours[/tex]