You buy 6 pounds of apples for $33. what is the cost of 10 pounds of apples

Write an equation involving two ratios.  The first ratio will be (6/10), which involves the weights of two different purchases of apples.  The second ratio will be ($33/x), which involves the selling prices of the purchases of apples.  Then

(6/10) = ($33/x).  Solve this for x, which will be the cost of 10 lb. of apples.

You may find this solution easier if you'd rewrite this equation as (10/6)=(x/$33).