give one example of when you would draw a diagram to solve an angle measurement problem

The parabola x = y² - 9 opens: a.)up b.)down c.) right d.)left

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.

:24% of students in a class are girls. if there are less than 30 students in this class, how many students are there? how many girls are there?