Correct Answer: –, –, ÷, =, ×, +

Solution : Given:
86 * 42 * 12 * 3 * 12 * 3 * 4

Let's check each option –
First option: +, –, ÷, ×, =, +
86 + 42 – 12 ÷ 3 × 12 = 3 + 4
L.H.S. = 86 + 42 – 12 ÷ 3 × 12
= 86 + 42 – 4 × 12
= 86 + 42 – 48
= 80
R.H.S. = 3 + 4 = 7
L.H.S. ≠ R.H.S.
Second option: –, –, ÷, =, ×, +
86 – 42 – 12 ÷ 3 = 12 × 3 + 4
L.H.S. = 86 – 42 – 12 ÷ 3
= 86 – 42 – 4
= 40
R.H.S. = 12 × 3 + 4 = 36 + 4 = 40
L.H.S. = R.H.S.
Third option: –, +, ÷, ×, =, +
86 – 42 + 12 ÷ 3 × 12 = 3 + 4
L.H.S. = 86 – 42 + 12 ÷ 3 × 12
= 86 – 42 + 4 × 12
= 86 – 42 + 48
= 92
R.H.S. = 3 + 4 = 7
L.H.S. ≠ R.H.S.
Fourth option: –, +, ×, =, ÷, +
86 – 42 + 12 × 3 = 12 ÷ 3 + 4
L.H.S. = 86 – 42 + 12 × 3 
= 86 – 42 + 36
= 80
R.H.S. = 12 ÷ 3 + 4 = 4 + 4 = 8
L.H.S. ≠ R.H.S.

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