Answer:
21 yards in 3 seconds
Explanation:
we give tracy the head start of 12 yards
then see how much she increases in 3 seconds at every second .
one second shes at 16 yards, 2 seconds she's at 20 yards & thats all the info we need
Alice runs 7 yards per second & we give her 3 seconds & how many yards she runs every second.
one second 7 yards , 2 seconds 14 yards & 3 seconds 21 yards & its at the 3 second that Alice has passed her.