Hello there!
Based from this question above, what this is asking is to find how much does 17% goes into 400 marbles.
We want to know how many marbles are in this 400 marbles. (This would be the key point)
We do (17% x 400).
By putting the "%" symbol this allows us the understand that we are trying to find out how many blue marbles they're going to be.
By multiplying them both together, we got our answer as (68) marbles.
Your correct answer would he 68.
I hope this helps you!