Answer:
[tex]\left \{ {{20x+30y=280} \atop {y=4x}} \right.[/tex]
Where [tex]x[/tex] is the number of small boxes sent and [tex]y[/tex] is the number of large boxes sent.
Step-by-step explanation:
Let be [tex]x[/tex] the number of small boxes sent and [tex]y[/tex] the number of large boxes sent.
Since each small box can hold 20 books ([tex]20x[/tex]), each large box can hold 30 books ([tex]30y[/tex])and altogether can hold a total of 280 books, we can write the following equation to represent this:
[tex]20x+30y=280[/tex]
According to the information provided in the exercise, there were 4 times as many large boxes sent as small boxes. This can be represented with this equation:
[tex]y=4x[/tex]
Therefore, the system of equation that be used to determine the number of small boxes sent and the number of large boxes sent, is:
[tex]\left \{ {{20x+30y=280} \atop {y=4x}} \right.[/tex]