How do you simplify and find the restrictions for (3x + 6 )/(5x+10)?

$\frac{3}{5}$, except when x=-2 in which case it will be an indeterminate form $\frac{0}{0}$.
The given expression is equivalent to$\frac{3 \left(x + 2\right)}{5 \left(x + 2\right)}$. Only exclusion is x=-2, because in that case the given expression becomes $\frac{0}{0}$ which is an indeterminate form.
For all other 'x' , the expression is equivalent to $\frac{3}{5}$