Rani's current age is 3 times that of her daughter. Mary 4 years ago, Rani s age was 4 times that of her daughter, what will be Mary's age 5 years from now?

Let the present age of Mary is x years.
$\therefore$The present age of Rani $=3x$ years
According to the question,
$$\begin{gathered} (x-4)\times 4=(3x-4) \\ \Rightarrow 4x-16=3x-4 \\ \Rightarrow x=12 years \end{gathered}$$
So, Mary's age is 5 years from now $=12+5$
$=17$ years