Final answer:
Bella's rate of return is 779%.
Step-by-step explanation:
To find Bella's rate of return, we can divide the total amount she had at the end of eight months ($879) by the amount she saved each month ($100).
This will give us the number of times her savings increased.
To calculate the rate of return, we subtract 1 from this value and convert it to a percentage:
Rate of return = ((Total amount / Amount saved) - 1) * 100
Rate of return = ((879 / 100) - 1) * 100
Rate of return = (8.79 - 1) * 100
Rate of return = 7.79 * 100
Rate of return = 779%