ANSWER : None of these

Explanation : . None of the interchanges is applicable in the equation to produce number 11.

ANSWER : x and -

Explanation : . If we interchange x and -, the equation changes into 3 x 9 – 27 + 9 ÷ 3 = 27 – 27 + 3 = 3. Hence, option (5) is the correct answer.

ANSWER : + and ÷

Explanation : . If we interchange signs + and ÷, then the equation results into 15 + 9 x 3 – 74 ÷ 2 = 15 + 27 – 37 = 5. Hence, option (3) is the correct answer.

ANSWER : None of these

Explanation : . 12 + 48 ÷ 8 – 4 x 4 = 12 + 6 – 16 = 2

ANSWER : + and x

Explanation : . Interchange of signs + and x makes the equation into 16 – 21 ÷ 7 + 6 x 3 = 16 – 3 + 18 = 31. Hence, option (2) is the correct answer.