By interchanging which two signs the equation will be correct?
$$9 \times 11 \div 31 + 62 - 13 = 18$$

Option (a) $$\times\ and\ \div$$

$$9 \div 11 \times 31 + 62 - 13 = 18$$

The given equation is not satisfied. Because it will give the values in fraction which is not possible. 

Option (b) $$-\ and\ \times$$

$$9 - 11 \div 31 + 62 \times 13 = 18$$

The given equation is not satisfied. Because it will give the values in fraction which is not possible.

Option (c) $$\div\ and\ +$$

$$9 \times 11 + 31 \div 62 - 13 = 18$$

The given equation is not satisfied. Because it will give the values in decimal which is not possible.

Option (d) $$+\ and\ \times$$

$$9 + 11 \div 31 \times 62 - 13 = 18$$

$$9+\frac{11}{31}\times62-13=18$$

$$9+11\times2-13=18$$

$$9+22-13=18$$

18=18

The given equation is satisfied. So this is the correct answer.