Respuesta :

caylus
hello,

Let's assume n the number searched.

nine less 3 times n is written 9-3n
 
[tex] \dfrac{9-3n}{4} =21\\ ==\ \textgreater \ 9-3n=84\\ ==\ \textgreater \ -3n=75\\ ==\ \textgreater \ n=-25 [/tex]