Hint: Look for numbers such as when multiplied by 3 equals less than 30 AND when multiplied by 6 equals greater than 40
Possible numbers:
7
7 x 3 = 21. It is less than 30.
7 x 6 = 42. It is greater than 40.
8
8 x 3 = 24. It is less than 30.
8 x 6 = 48. It is greater than 40.
9
9 x 3 = 27. It is less than 30.
9 x 6 = 54. It is greater than 40.
So, sum = 7 + 8 + 9 = 24
