Setting up the equations to solve is the toughest part of this problem. The variable we are trying to solve for is the number of hours it takes for them to run the same distance (that's when they will meet). Let's call that variable "x".
Now, we can write one equation for the number of miles Jessie runs:
10x (where 10 is miles/hour, x is hours. miles/hour * hour gives miles)
The equation for the number of miles Jim runs is:
7x + 2*7. The 7x term is similar to the description above (miles/hour * hours = miles). The 2*7 comes in from the fact that Jim got a 2 hour head start. 2 hour head start running at 7 miles per hour gives 2*7 = 14 mile head start.
We can set these two equations equal to eachother, since we want the distance in miles that they both run to be the same: 10x = 7x + 14. Simplifying, we get 3x = 14. Therefore, x (the number of hours until they meet) = 14/3