Ok, first set this up as an equation with your given variables. You know that Sylvie bought 1 container of cream cheese, which is $2.95, and you know that Sylvie spent $7.50 (my best assumption is this is the subtotal) on the cream cheese and 13 bagels. As an equation, it would come out as:
[tex]7.50=2.95+13(b)[/tex]
To start solving the algebraic equation, wou can subtract 2.95 on both sides, resulting as
[tex]4.55=13 (b)[/tex]
Now, to get "b" by itself, you must divide 13 on both sides, resulting as
[tex].35=b[/tex]
This will answer your question as the cost of 1 bagel would be $0.35 per bagel.