suppose g(m) varies inversely with M and g(m)=3.5 when m=10. what is the value of M when g(m)=5?

In an inverse variation, the function takes the form xy=k
where k is a constant.
Given g(10)=3.5, we find k=xy=3.5*10=35.  
This means the function is
m*g(m)=35
When g(m)=5, then m=35/5=7.