Correct Answer: +, −, ÷, ×

Solution : Given:
66 * 6 * 12 * 3 * 15 = 12

Let's check the options –
First option: ÷, −, ×, +
⇒ 66 ÷ 6 – 12 × 3 + 15 = 12
Solving the L.H.S. of the equation –
= 66 ÷ 6 – 12 × 3 + 15
= 11 – 12 × 3 + 15
= 11 – 36 + 15
= 26 – 36
= –10 ≠ 12
Second option: +, −, ÷, ×
⇒ 66 + 6 – 12 ÷ 3 × 15 = 12
Solving the L.H.S. of the equation –
= 66 + 6 – 12 ÷ 3 × 15
= 66 + 6 – 4 × 15
= 66 + 6 – 60
= 72 – 60
= 12
Third option: ÷, ×, +, −
⇒ 66 ÷ 6 × 12 + 3 – 15 = 12
Solving the L.H.S. of the equation –
= 66 ÷ 6 × 12 + 3 – 15
= 11 × 12 + 3 – 15
= 132 + 3 – 15
= 135 – 15
= 120 ≠ 12
Fourth option: ×, −, ÷, +
⇒ 66 × 6 – 12 ÷ 3 + 15 = 12
Solving the L.H.S. of the equation –
= 66 × 6 – 12 ÷ 3 + 15
= 66 × 6 – 4 + 15
= 396 – 4 + 15
= 411 – 4
= 407 ≠ 12

So, only the second option satisfies the given equation. Hence, the second option is correct.