Answer: (s for small, l for large) s=15.25 kg, l=18.5 kg.
Explanation: We need a system of equation to find the two weights of both boxes.
We can use 4s+8l=209 and 2s+3l=86.
If we multiply the second equation by -2 (for elimination), we will have -4s-6l=-172.
Combing the first equation with this new one gives us 2l=37, where dividing by 2 gives us l=18.5 kg.
We can plug 18.5 into any of the two original equations to find s.
4s+8*18.5=209
4s+148=209
4s=61
s=15.25 kg
