This is what I observed

The first 2 terms are taken as 1,2

Now for the third term 1+2 = 3.

For the 4th term = 1+2+3 = 6.

For the 5th term though we must take the sum of only the last 2 terms again as we did for the 3rd term

So 5th term = 6 + 3 = 9.

6th term = 9 + 6 + 3 = 18 ===> 8 [ only units place is retained ]

Now for the 7th term, again we have to take the sum of only the last 2 terms => 8 + 9 = 17 = 7.

Finally the answer is 9 + 8 + 7 = 24 ===> **4**