Alright, Angel, I promise this is easier than it seems!
1. The two variables are the time and distance. The dependent variable is just like the name sounds; it's dependent on the independent variable.
Now, does the time he's racing depend on the distance he travels? Of course not, it's the other way around. The more or less time, the more or less he travels. Thus, the distance is the dependent variable and the time is the independent variable.
The domain is the limits of your independent variable. The starting time would be 0 and his finishing time would be 100 minutes, since it takes 2 minutes to go 1 km and he has to travel 50. Your domain is (0,100).
The range is the limits of your dependent variable. It should be easy to figure out that this is (0,50).
2. The -1/4 slope represents his distance going DOWN from 30 km away to 0 as he gets to where he is going. Remember that we are counting backwards since he is measuring distance TO the end point and not distance from the starting point. Every minute, the distance to 30 km away decreases by 1/4 mile.
Remember that y=0 all along the x-axis. We then substitute 0 for f(t).
0 = 30 - 1/4t
-30 = -1/4t
t = 120
What does it mean when the function equals 0? He's reached the 30 km mark!
The last question is tricky. Technically, no, they shouldn't pass each other, since Frank is going faster than Jamal from the start.
