Hello,

The given series is 5, 10, 17, 26,..

The difference between the first and second terms is 5.

Similarly the difference between third and second terms is 7.

And the difference between fourth and third terms is 9.

So the differences between terms is a series 5, 7, 9,.. with 2 as a common difference.So the difference between fifth and fourth term will be 11.Which implies that the fifth term will be 26+11=37.

Hope this helps!!