Notice that they give us the actual linear equation that represents the savings of Jim for week:
y = 120 x + 250
The rate here is given by the "slope"of this linear equation (the slope is the numerical factor that multiplies the variable "x" of the number of weeks).
Then the RATE of savings per week for Jim is: $120 per week.
Now, we need to obtain the rate for Josh based on the values given in the table. We use for example:
2 weeks --> $520
4 weeks --> $740
and we calculate the rate using the slope formula:
rate per week for Josh = (740 - 520) / (4 - 2) = 220 / 2 = $110 per week.
Then, Vivian is right (Jim is saving at a higher rate)