Let
x--------> the number of months
y-------> represents the balance, in dollars, of a bank account
we know that
y=-50x+100
the rate of change is equal to the slope of the line
so

therefore
<u>the answer is</u>
the rate of change is 
Try this solution, it consists of two parts (MN=8).
Evaluation of square root 169 = 13, so 10 + 13 = 23