Please I need your help ASAP

Liam's parents are driving three times as fast as liam is biking, but they left later than he did. if his parents caught up with him two hours after he left, how much later than liam did they leave?

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.

Use composition to determine if (x) or h(x) is the inverse of f(x) for the limited domain x2-1.