value x as the weight of the large box, y as the weight of the small box
7x + 9y = 157 (1)
5x + 3y = 89 -> 15x + 9y = 267 (2)
(2) - (1) => 8x = 110
=> x = 13.75 kg
=> (1) => 5x13.75 + 3y = 89 => 3y = 20.25 => y = 6.75 kg
So, large box weigh 13.75 kg, and small box weigh 6.75 kg
Mark Brainliest if correct. :D