Arecipe requires 13 ounces of sugar and 18 ounces of flour. if only 10 ounces of sugar are used, how much flour, to the nearest ounce, should be used? (a) 13 (b) 23 (c) 24 (d) 14 (e) 15

We can list the amount of sugar and flour required into ratios then solve the questions by fractions. 

From the given information, the ratio of the amount of sugar to the amount of flour needed in the recipe should be 13:18.
This ratio can also be written as 13/18.

In the question, the ratio should not be changed, just that the amount of each turns different. 

So, let y be the amount of flour needed. 
13/18 = 10/y
Use cross method to solve this,
18 x 10 = 13y
180 = 13y
y = 180/13
y = 13.8461538462
the answer should be 13.8461538462 ounces, 
and round to the nearest ounce, 
the answer should be D, 14.

What class is this? i have no idea and i'm not going to give you the wrong answer. do you have a graph that goes with all the questions