Fifteen years from now, Ravi’s age will be four times his present age. What is Ravi’s present age?

Let the present age of Ravi be $x$.  

Fifteen years later, Ravi’s age will be $x + 15$. According to the question:

$x + 15 = 4x$
$\Rightarrow 4x - x = 15$
$\Rightarrow 3x = 15$
$\Rightarrow x = \dfrac{15}{3}$
$\Rightarrow x = 5$

Therefore, the present age of Ravi = $5$ years.

मान लीजिए रवि की वर्तमान आयु $x$ वर्ष है।  

पंद्रह वर्ष बाद, रवि की आयु = $x + 15$। प्रश्न के अनुसार:

$x + 15 = 4x$
$\Rightarrow 4x - x = 15$
$\Rightarrow 3x = 15$
$\Rightarrow x = \dfrac{15}{3}$
$\Rightarrow x = 5$

अतः रवि की वर्तमान आयु = $5$ वर्ष