Explain how estimating you check the reasonableness of your answer

Me find the measure to side a and the process to solve the problem you appreciate it : )

You and a friend race across a field to a fence and back. your friend has a 50-meter head start. the equations shown represent you and your friend's distances dd (in meters) from the fence tt seconds after the race begins. find the time at which you catch up to your friend. you: d=∣−5t+100∣d=∣−5t+100∣ your friend: d=∣−313t+50∣∣

Lydia collected two sets of data one set of data shows an outlier. which set has an outlier, and which number is the outlier?