Compute the following limits$,$ if possible. You may use L'Hospital's $($Bernoulli$\text{'}$s$)$ rule if it applies. If a limit doesn't exist, answer DNE. If a limit is $$ or $-,$ then answer $$ or $-.$

$($a$)\underset{x0}{lim}\frac{x}{sin7x}=$

$($b$)\underset{x}{lim}\frac{x}{sin7x}=$

$($c$)\underset{x9}{lim}\frac{x-9}{x^{\frac{1}{2}}-3}=$