Correct Answer: 6 and 7

Solution : Given:
5 × 7 – 4 + 21 ÷ 6 = 29

Replace the given numbers in the options with the original numbers in the given equation.
First option: 6 and 5
Solving the L.H.S. of the equation –
= 6 × 7 – 4 + 21 ÷ 5
= 6 × 7 – 4 + 4.2
= 42 – 4 + 4.2
= 42.2 ≠ 29
Second option: 6 and 7
Solving the L.H.S. of the equation –
= 5 × 6 – 4 + 21 ÷ 7
= 5 × 6 – 4 + 3
= 30 – 4 + 3
= 29 = R.H.S.
Third option: 21 and 29
5 × 7 – 4 + 29 ÷ 6 = 21
Solving the L.H.S. of the equation –
= 5 × 7 – 4 + 29 ÷ 6
= 5 × 7 – 4 + 4.83
= 35 – 4 + 4.83
= 35.83 ≠ 21
L.H.S ≠ R.H.S
Fourth option: 5 and 4
Solving the L.H.S. of the equation –
= 4 × 7 – 5 + 21 ÷ 6
= 4 × 7 – 5 + 3.5
= 28 – 5 + 3.5
= 26.5 ≠ 29

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