Jason and Glenn have some balls with them.
Suppose J = the number of Balls Jason has
Suppose G = the number of balls Glenn has
If Jason gives one ball to glenn,
Then Jason will have J-1 balls and Glenn will have G+1 balls.
then both will have equal number of balls,
So
J-1 = G+1
but if glenn gives 1 ball to Jason,
Then Glenn will have G-1 balls and Jason will have J+1 balls.
then Jason will have 2 times the number of balls glenn has.
So J+1 = 2(G-1)
so how many balls do they have?
We have this system of two equations in two unknowns:
J-1 = G+1,J+1 = 2(G-1)
Simplify each and get
J- G = 2
J-2G = -3
Solve and get Jason had 7 and Glenn had 5 to start with.
Checking:
If Jason gives one ball to glenn, then both will have equal number of balls
Jason would have 6 and and Glenn would have 6. That checks.
but if glenn gives 1 ball to Jason, then Jason will have 2 times the number of balls glenn has.
Glenn would have 4 and Jason would have 8. That checks.
Edwin