Find the gcf for 15az and 25az

Find the greatest common factor of the followig monomials 21u^5v,3u^4v^6, and 3u^2v^5

Ascientist wants to use a model to present the results of his detailed scientific investigation. why would a model be useful? a )because the model makes the concepts easier to understand b) because the model is easy to put together and to use c) because the model prevents other scientists from asking questions d) because the model requires the audience to pay full attention to it i don't know what to choose because between a and d a is much more likely than d because it only wants to get the attention of the audience. i'm confuse.

When 142 is added to a number the result is 64 more then 3 times the number. option 35 37 39 41