Answer:
Large box's weight = 18.5 kilogram
small box's weight = 6.5 kilogram
Explanation:
We need to make equation to get the weigh of each box.
Let,
Large box = l
Small box = s
According to the question,
2l + 12s = 115 ........... (i)
Again, 5l + 3s = 112 ........ (ii)
From equation (i), we can say that,
or, 2l = 115 - 12s [changing the side]
or, l =
[divide both the sides by 2] ........ (iii)
Putting the value of "l" in equation (ii), we get,
5l + 3s = 112
or, 5 ×
+ 3s = 112
or,
+ 3s = 112
or,
= 112
or, 575 - 54s = 112 × 2 [multiplying by 2]
or, 575 - 54s = 224
or, -54s = 224 - 575 [changing the side]
or, -54s = -351
or, s =

or, s = 6.5
Putting the value of "s" in equation (iii),
l =

or, l =

or, l = 37 ÷ 2
l = 18.5
Therefore, large box = 18.5 kilogram
small box = 6.5 kilogram