Answer:
Large box:

Small box:

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:

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":

Finally, susbstitute the value of "l" into any original equation and solve for "s":
