We can compare how much they would run if they ran 1 hour.
Chris ran 3 miles in 30 minutes, which means he ran 1 mile in 10 minutes (at a constant speed).
He'll run 6 miles in 1 hour.
Elizabeth ran 6 miles in 50 minutes. That means she ran 1 mile in 8.3 minutes (at a constant speed).
She'll run a little over 7 miles in 1 hour.
So, Elizabeth ran faster than Chris.
I really hope this helped you out! c:
