Answer: 20 weeks
I forgot to make the rate of change negative but it is the same either way so ignore the explanation
Step-by-step explanation: You can represent the 2 bank accounts with equations, with y being the cost and x being the number of weeks.
Jim's equation is

Sally's equation is

Now you can solve by substitution for x. Since y= sally's equation and y= Jim's equation you can use the transitive property to say that Jim's equation = sally's equation.

Subtract 20x from both sides

Subtract 1250 from both sides

Divide both sides by 7.5

After 20 weeks they will have the same amount of money