If x stand for -, ÷ stands for +, + stands for ÷ and - stands for x, then arrange the following in increasing order :
1. 15 - 5 ÷ 5 x 20 + 10
2. 8 ÷ 10 - 3 + 5 x 6
3. 6 x 2 + 3 ÷ 12 - 3
4. 3 ÷ 7 - 5 x 10 + 3
Choose the correct answer from the code given below :

The correct answer is (B) 2, 4, 3, 1.

Step-by-step operator replacement & evaluation:

• Operator replacement rules: $\times \to -,÷\to +,+\to ÷,-\to \times$$\times$ \to -, \; $\div$ \to +, \; + \to $\div$, \; - \to $\times$.
• Expression 1: $15$$\times$ 5 + 5 - 20 $\div$ 10 = (15 $\times$ 5) + 5 - (20 $\div$ 10) = 75 + 5 - 2 = 78.
• Expression 2: $8 + 10$$\times$ 3 $\div$ 5 - 6 = 8 + (10 $\times$ 3 $\div$ 5) - 6 = 8 + 6 - 6 = 8.
• Expression 3: $6 - 2$$\div$ 3 + 12 $\times$ 3 = 6 - (2 $\div$ 3) + (12 $\times$ 3) = 6 - 0.67 + 36 = 41.33.
• Expression 4: $3 + 7$$\times$ 5 - 10 $\div$ 3 = 3 + (7 $\times$ 5) - (10 $\div$ 3) = 3 + 35 - 3.33 = 34.67.
• Arranging in increasing numerical order: $\text{Expression 2 }(8)<\text{Expression 4 }(34.67)<\text{Expression 3 }(41.33)<\text{Expression 1 }(78)⟹<strong>2,4,3,1<\mathrm{/}strong>$$\text{Expression 2 }$ (8) < $\text{Expression 4 }$ (34.67) < $\text{Expression 3 }$ (41.33) < $\text{Expression 1 }$ (78) $\implies$ <strong>2, 4, 3, 1</strong>.