The problem is invalid. ANY number in the missing spot will make a valid sequence. It is impossible to know "the right" answer.
This kind of problem can provide some good mental exercise in looking for a reasonable pattern in the given numbers. But it is pointless to spend a lot of time on them, or to worry about not being able to "solve" them, because there is no way of knowing whether an answer you come up with is "right".
For this example, the given numbers are strictly increasing, so the missing number is PROBABLY between 22 and 40.
If we choose 31, then we get a nice pattern in the differences between successive terms:
7 10 16 22 31 40 52
3 6 6 9 9 12
So "31" might be a good GUESS for the missing number....
But we don't know if it is "right"....