Correct Answer: 12 and 3

Solution : Given:
108 ÷ 3 – 126 ÷ (5 × 3 + 12) + 4 = 11

Interchange the numbers as given in the options.
First option: 11 and 12
After interchanging the numbers the equation becomes –
⇒ 108 ÷ 3 – 126 ÷ (5 × 3 + 11) + 4 = 12
⇒ 108 ÷ 3 – 126 ÷ (26) + 4
⇒ 36 – 4.84 + 4
⇒ 35.16 ≠ 12
Second option: 12 and 3
After interchanging the numbers the equation becomes –
⇒ 108 ÷ 12 – 126 ÷ (5 × 12 + 3) + 4 = 11
⇒ 108 ÷ 12 – 126 ÷ (63) + 4
⇒ 9 – 2 + 4 = 11
⇒ 11 = 11 (L.H.S. = R.H.S.)
Third option: 12 and 4
After interchanging the numbers the equation becomes –
⇒ 108 ÷ 3 – 126 ÷ (5 × 3 + 4) + 12 = 11
⇒ 108 ÷ 3 – 126 ÷ (19) + 12
⇒ 36 – 6.63 + 12
⇒ 41.37 ≠ 11
Fourth option: 126 and 108
After interchanging the numbers the equation becomes –
⇒ 126 ÷ 3 – 108 ÷ (5 × 3 + 12) + 4 = 11
⇒ 126 ÷ 3 – 108 ÷ (27) + 4
⇒ 42 – 4 + 4
⇒ 34 ≠ 11

So, only the second option satisfies the R.H.S. of the equation. Hence, the second option is correct.