first box:32kg
second box:96kg
Explanation:
Using principle of linear equation, we can make the two boxes be represented by the variables "x" & "y"
The total amount of kg within the two boxes:128kg so becomes
the x plus y equal to 128 but one is 3 times more than the other so y becomes equals to 3x so equation is
x plus 3x equals to 128
4x equals 128,dividing both sides by 4
x equals to 32 so 1st box is 32kg
y equals 3x so 3(32) equals to 96, making 2nd box becoming 96kg