Seven white circles are in a row. How many ways are there to color 3 circles blue so that 2 blue circles are never next to each other?

Question

I need the answer

Answer 1

3 of 7, but no 2 together

BNBNBN

NBNBNB

2 ways to put 3 Blues in a row of 6, with no 2 blues together

but you want 7 in a row, so there's more

BNBNBNN

BNBNNBN

BNBNNNB

3 ways with B at the front

NBNBNBN

NBNBNNB

2 ways with B 2nd

NNBNBNB

1 way with B 3rd

Total ways= 3+2+1 = 6