There can be no generalisation about mathematicians or any other professions. Even some authors are not good writers!
The answer to this is a highly variable one. Normally, as one assumes, mathematicians, just because they are good at numbers, may not always land them up being poor writers. However, it is quite true, that because mathematicians, often busy with calculations, may not have been able to work much on their literary skills. Hence, one may face some problem with the language and editing. But, this isn't a bi problem, as this applies to most other professions. So, on a whole, mathematicians can be excellent writers, if suitable efforts can be put forward.
it will be unwise to think that engineering is for good mathematicians who cant write essays, some are great writers it depend from individual to individual
No, not at all.
no
The writers of the math books are the ones who think up those questions, they are generally mathematicians.
Dogs aren't generally mathematicians.
Study math! it is good for you and it can lead you to jobs that are not communication heavy.
On average they are as good or as bad as the general public.
No, this is far from the truth. I am one of those people working in a math related field.
Generally not.
Generally they are excellent.
Mathematicians are people who are 'experts' at Math.