Solve the initial value problems.

$($a$)x^{\text{'}}\frac{5}{t}x=1t,x(1)=1$;

$($b$)cos{v}^{\text{'}}v=3,v(\frac{}{2})=1$;

$($c$)x^{\text{'}}\frac{e^{-t}t}{x}=t,x(1)=0$;

Please solve all! Especially B