Correct Answer: −, +, ×, ÷, ×, ×, =

Solution : Given:
[{(32 % 28) % (6 % 4)} % (1 % 7)] % 5 % 20

Replace % with the mathematical signs and solve the equations one by one using BODMAS.
Let's check the given options –
First option: −, +, ×, ÷, ×, ×, =
⇒ [{(32 − 28) + (6 × 4)} ÷ (1 × 7)] × 5 = 20
Solving the L.H.S of the equation –
= {(4 + 24) ÷ 7} × 5
= (28 ÷ 7) × 5
= 20
Second option: ×, ÷, ×, ×, −, +, =
⇒ [{(32 × 28) ÷ (6 × 4)} × (1 − 7)] + 5 = 20
Solving the L.H.S of the equation –
= {(896 ÷ 24) × (−6)} + 5
= −224 + 5
= −219 ≠ 20
Third option: ×, −, +, ×, ÷, ×, =
⇒ [{(32 × 28) − (6 + 4)} × (1 ÷ 7)] × 5 = 20
Solving the L.H.S of the equation –
= {(896 − 10) × 0.14} × 5
= {886 × 0.14} × 5
= 124.04 × 5
= 620.2 ≠ 20
Fourth option: −, +, ×, ×, ×, ×, =
⇒ [{(32 − 28) + (6 × 4)} × (1 × 7)] × 5 = 20
Solving the L.H.S of the equation –
= {(4 + 24) × (7)} × 5
= {28 × 7} × 5
= 196 × 5
= 980 ≠ 20

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