Sara walks from her home to the store. Halfway to the store, she realizes that she forgot to bring money, so she returns around, returns home, gets her money, and then walks all the way to the store. Graph time on the horizontal axis and distance on from home on the vertical axis.

We won't just do your homework for you. You need to first show that you're trying to do this yourself. So, how do you think the graph should look?

The problem is I don't even understand how to do it.

OK, here's how to get started. You're going to plot time along the horizontal axis (the X axis), starting at time T=0 at the left, and distance on the vertical axis (the Y axis) going up the left side of the graph. Sara starts at home at time t=o, so make a dot on the graph at this point (0,0). Make a tick mark on the vertical axis at the x-intercept and call it "Home" make another mark near the top of the vertical axis and mark it "Store." Then make another tick mark on the vertical axis half-way between "Home" and "Store" and call this "Half Way." Now let's look at the horizontal axis. First mark the intercept point between the X and Y axis as T=0. Then mark a point on the horizontal axis perhaps 1/4 of the way along, and call this point T1. Now, you know that Sara walks from home to the half-way point - if you call the amount of time it takes her to do that T1, then all you need to do is draw a straight line from the origin (i.e. she starts at home at time T=0) to the half-way point at time T1. You've just plotted the first part of her journey. Can you do the rest?