Respuesta :

Answer:

D) 39

Step-by-step explanation:

[tex]||\text{c}\bold{u}||=||3\langle5,12\rangle||=||\langle3*5,3*12\rangle||=||\langle15,36\rangle||=\sqrt{15^2+36^2}=\sqrt{225+1296}=\sqrt{1521}=39[/tex]