How to rewrite 9/10 and 23/25 so they have common denominators

Which one ? is the answer and how to find this answer

One file clerk can file 10 folders per minute. a second file clerk can file 11 folders per minute. how many minutes would the two clerks together take to file 672 folders?

The change in water level of a lake is modeled by a polynomial function, w(x). described how to find the x-intercepts of w(x) and how to construct a rough graph of w(x) so that the parks department can predict when there will be no chage in the water level. you may create a sample polynomial of degree 3 or higher to use in your explanations.