Answer:
Large box: [tex]18.5\ kilograms[/tex]
Small box: [tex]15.25\ kilograms[/tex]
Step-by-step explanation:
Let be "l" the weight in kilograms of a large box and "s" the weight in kilograms of a smalll box.
Set up a system of equations:
[tex]\left \{ {{3l+2s=86} \atop {8l+4s=209}} \right.[/tex]
In order to solve the system of equations, you can apply the Elimination Method. Multiply the first equation by -2, add the equations and then solve for "l":
[tex]\left \{ {{-6l-4s=-172} \atop {8l+4s=209}} \right.\\......................\\2l=37\\\\l=\frac{37}{2}\\\\l=18.5[/tex]
Finally, susbstitute the value of "l" into any original equation and solve for "s":
[tex]3(18.5)+2s=86\\\\2s=86-55.5\\\\s=\frac{30.5}{2}\\\\s=15.25[/tex]