Which two numbers need to be interchanged to make the given equation correct?
$$16 \times 1792 \div 7 + 9 - 15 = 778$$

Option (a) 15, 9

$$16\times1792\div7+15-9=778$$

$$16\times256+6=778$$

4096+6=778

$$4102\ne778$$

The given equation is not satisfied. So this will not be the correct answer.

Option (b) 16, 7

$$7 \times 1792 \div 16 + 9 - 15 = 778$$

$$7\times\frac{1792}{16}+9-15=778$$

$$7\times112+9-15=778$$

784-6=778

778=778

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

Option (c) 16, 15

$$15 \times 1792 \div 7 + 9 - 16 = 778$$

$$15 \times 256 + 9 - 16 = 778$$

3840-7 = 778

$$3833\ne\ 778$$

The given equation is not satisfied. So this will not be the correct answer.

Option (d) 16, 9

$$9 \times 1792 \div 7 + 16 - 15 = 778$$

$$9 \times 256 + 16 - 15 = 778$$

2304+1 = 778

$$2305\ne\ 778$$

The given equation is not satisfied. So this will not be the correct answer.