Why might working on a commission basis make dealing with finances more difficult

The class wants to raise a total of $750.if they receive a profit of $1.25 from each candybar sold, how many bars must they sell to reachtheir goal

Josephine has a great garden with and area of 2x2 + x - 6 square feet

Ascientist wants to use a model to present the results of his detailed scientific investigation. why would a model be useful? a )because the model makes the concepts easier to understand b) because the model is easy to put together and to use c) because the model prevents other scientists from asking questions d) because the model requires the audience to pay full attention to it i don't know what to choose because between a and d a is much more likely than d because it only wants to get the attention of the audience. i'm confuse.