If you look at the number of stars in each box you get:
2, 4, 6, 8
So this is an arithmetic sequence with a common difference with each term being 2 greater than the previous term.
Any arithmetic sequence can be expressed as:
a(n)=a+d(n-1), a=initial term, d=common difference, n=term number
In this case a=2 and d=2 so
a(n)=2+2(n-1) which can be simplified
a(n)=2+2n-2
a(n)=2n
So the fifth term in the sequence is:
a(5)=2(5)
a(5)=10