1/3 x 60 = 20 mins
Carl walks the dog for 20 mins in the morning.
1/2 x 60 = 30 mins
Carl walks the dog for 30 mins in the afternoon.
20 + 30 = 50 mins
Carl walks the dog for 50 mins a day.
50 x 7 = 350 mins
Carl walks the dog for 350 mins a week.
Answer: 350 mins.
Is the goal to simplify? You just need to multiply the exponents for each factor:
(2z^2)^(-3)
= 2^(-3) x z^(2 x -3)
= (1/2)^3 x z^(-6)
= (1/8) x (1/z)^6
= 1/(8z^6)
