Exponential rules state that when you divide exponents, you subtract by the powers. The powers have the same coefficients, so you can divide the two numbers.
6 - (-3) = 9
The answer is

.
Answer:
With Riley's pattern, he will practice 2,000 total minutes in 25 days.
Step-by-step explanation:
Since Riley increased his practice time by 20, 20 times 40 is 80 minutes. And since he is repeating this in total of 25 days, 80 times 25 is 2,000.
Hope this helped you in some way. If not, then let me know.