Answer:
It will take him 1 hour and 30 minutes. (90 minutes)
Step-by-step explanation:
If he is running 1 mile in 10 minutes and he needs to run 9 miles the just multiply 9 by 10 to get 90 then simplify if you need to to get 1 hour and 30 minutes.
Hope this helped and have a great rest of your day.
Answer:

Step-by-step explanation:
when the exponent is equal, we can put the x and y together in a bracket and a as the Exponent of xy.
Hope I get your question~
Given:
Polynomials
To find:
Monomial of 2nd degree with leading coefficient 3
Solution:
Monomial is an algebraic expression with only one term.
Option A: 
It is not a monomial because it have 2 terms.
It is not true.
Option B:
It is not a monomial because it have 2 terms.
It is not true.
Option C: 
It have one term only. So, it is a monomial.
Degree means highest power. So degree = 2
Leading coefficient means the value before variable.
Leading coefficient = 3
It is true.
Option D: 
It have one term only. So, it is a monomial.
Degree means highest power. So degree = 3
It is not true.
Therefore
is a monomial of 2nd degree with a leading coefficient of 3.
I think the answer is 12.8 mm