We can make a table for better understanding.
$\begin{array}{lcc} & \text{Pencil} & \text{Sharpeners} \\ \text{Aron:} & a & b \\ \text{Aditya:} & 2a & b-10 \\ \text{Cost of:} & ₹x & ₹(x+2) \end{array}$
The total amount of money spend by Aron is same as Aditya. Then,
$ax + b(x+2) = 2ax + (b – 10)(x+2)$
$ \Rightarrow ax + bx + 2b = 2ax + bx + 2b – 10x – 20$
$ \Rightarrow 10x + 20 = ax$
$ \Rightarrow \boxed{a = \frac{20}{x} + 10} \quad \longrightarrow (1)$
The minimum number of pencils bought by Aron and Aditya together $ = a + 2a = (3a)_{\text{min}}$
From equation $(1),$
$a = \frac{20}{x} + 10 $
$ \Rightarrow a_{\text{min}} = \frac{20}{20} + 10 \quad [\because \text{Maximum value of}\; x = 20]$
$ \Rightarrow \boxed{a_{\text{min}} = 11}$
$\therefore (3a)_{\text{min}} = 3 \times 11 = 33.$
Correct Answer $: \text{B}$