Correct Answer: 12 and 4, ÷ and ×

Solution : Given:
24 – (9 ÷ 12) + (84 × 4) + 28 = 23

Interchange the given signs and numbers in the options one by one with the original signs and numbers in the given equation.

Let's check the options –
First option: 24 and 28, – and ÷
= 28 ÷ (9 – 12) + (84 × 4) + 24
= 28 ÷ (–3) + (336) + 24
= –9.3 + 336 + 24
= 350.7 ≠ 23
Second option: 24 and 28, × and ÷
= 28 – (9 × 12) + (84 ÷ 4) + 24
= 28 – (108) + (21) + 24
= –35 ≠ 23
Third option: 9 and 4, ÷ and ×
= 24 – (4 × 12) + (84 ÷ 9) + 28
= 24 – (48) + (9.3) + 28
= 13.3 ≠ 23
Fourth option: 12 and 4, ÷ and ×
= 24 – (9 × 4) + (84 ÷ 12) + 28
= 24 – (36) + (7) + 28
= 23

So, only the fourth option satisfies the equation. Hence, the fourth option is correct.