I the week starts on Monday he will fill Monday and Saturday and on each Monday he will wash his car
Solution:
Given:

The value of a car after t - years will depreciate.
Hence, the equation given represents the value after depreciation over t-years.
To get the rate, we compare the equation with the depreciation formula.

Hence,

Therefore, the value of this car is decreasing at a rate of 6%. The purchase price of the car was $16,300.
(number of yellow marbles) / (overall number of marbles)
=
2/20
The answer to your question is 3