Respuesta :

[tex]\begin{gathered} \text{ If we note by "x" our number, then} \\ 0.75\cdot x-0.2x=378.9 \\ (0.75-0.2)x=378.9 \\ 0.55x=378.9 \\ x=\frac{378.9}{0.55} \\ x=688 \end{gathered}[/tex]

Thus, the 40% of the number is

[tex]688.909\cdot0.4=275.563[/tex]