Question

what is the next number in the sequence: 3, 8, 18, 38...?

Answer 1

It would be 2 times the number before plus 2
so
38(2)+2
78

78 would be it

Answer 2

Look at the differences between each term. Is there a clear pattern there?

Answer 3

Yup,
3(2)+2=8
8(2)+2=18
18(2)+2=38

So 38(2)+2=78

@DDCamp