Answer: 100

Explanation:
The pattern is 23, 33, 43, 53, 63, 73. But, 100 is not a perfect cube. 

Answer: 28

Explanation:
Each of the numbers except 28, is a multiple of 3. 

Answer: 55

Explanation:
Add 5, 7, 9, 11, 13, 15.

Answer: 18.5

Explanation:
The terms are alternatively multiplied by 1.5 and divided by 3. However 18.5 does not satisfy it

Answer: 634

Explanation:
Alternately, 23 is added and 17 is subtracted from the terms. So. 634 is wrong

Answer: 24

Explanation:
The terms are alternately successively divided by 12, 10, 8, 6, …. Etc. So 24 is wrong.

Answer: 124

Explanation:
The numbers are 13, 23, 33, 43, etc. So, 124 is wrong. It must have been 53 i.e 125.

Answer: 9

Explanation:
Terms at odd places are 5, 6, 7, 8 etc. and each term at even place is 16. So, 9 is wrong.

Answer: 40

Explanation:
The difference between two successive terms from the begininning are 7, 5, 7, 5, 7, 5. So 40 is wrong.

Answer: 150

Explanation:
The numbers are 7 * 8, 8 * 9, 9 * 10, 10 * 11, 11 * 12, 12 * 13. So, 150 is wrong.