When the problem says "a number", it refers to a variable which we are going to call n.
So, the expression would be
[tex]n+n+2n+4n=104[/tex]Now, we reduce all like terms
[tex]8n=104[/tex]Then, we divide the equation by 8
[tex]\begin{gathered} \frac{8n}{8}=\frac{104}{8} \\ n=13 \end{gathered}[/tex]