ANSWER
It took 1 hour 30 minutes
EXPLANATION
It was given that Elena and Jada are 12 miles apart.
This means that the distance between them is
![d = 12 \: miles](https://tex.z-dn.net/?f=d%20%3D%2012%20%5C%3A%20miles)
We use the formula,
![speed = \frac{distance}{time}](https://tex.z-dn.net/?f=speed%20%3D%20%5Cfrac%7Bdistance%7D%7Btime%7D%20)
If Elena covers d miles in
![t_1 \: hours](https://tex.z-dn.net/?f=t_1%20%5C%3A%20hours)
Then Jada will cover,
![( 12-d) \: miles](https://tex.z-dn.net/?f=%28%2012-d%29%20%5C%3A%20miles)
in
![t_2 \: hours](https://tex.z-dn.net/?f=t_2%20%5C%3A%20hours)
We were told that Elena runs at a constant speed of 5 miles per hour.
This implies that,
![5 = \frac{d}{t_1}](https://tex.z-dn.net/?f=5%20%3D%20%5Cfrac%7Bd%7D%7Bt_1%7D%20)
![t_1= \frac{d}{5} ...eqn1](https://tex.z-dn.net/?f=t_1%3D%20%5Cfrac%7Bd%7D%7B5%7D%20...eqn1)
and Jadda walks a constant speed of 3 miles per hour.
This implies that,
![3 = \frac{12-d}{t_2}](https://tex.z-dn.net/?f=3%20%3D%20%5Cfrac%7B12-d%7D%7Bt_2%7D%20)
This implies that,
![t_2 = \frac{12-d}{3} ...eqn2](https://tex.z-dn.net/?f=t_2%20%3D%20%5Cfrac%7B12-d%7D%7B3%7D%20...eqn2)
When Elena and Jada meets,then
![t_2 = t_1](https://tex.z-dn.net/?f=t_2%20%3D%20t_1)
We equate the two equations and solve. This implies that,
![\frac{d}{5} = \frac{12-d}{3}](https://tex.z-dn.net/?f=%20%5Cfrac%7Bd%7D%7B5%7D%20%3D%20%5Cfrac%7B12-d%7D%7B3%7D)
We cross multiply to get,
![3d = 5(12-d)](https://tex.z-dn.net/?f=3d%20%3D%205%2812-d%29)
![3d = 60-5d](https://tex.z-dn.net/?f=3d%20%3D%2060-5d)
This implies that,
![8d= 60](https://tex.z-dn.net/?f=8d%3D%2060)
![d = 7.5](https://tex.z-dn.net/?f=d%20%3D%207.5)
The time they met was after