It takes 12 minutes to copy the old and the new together.
In other words, an old copy takes 48 minutes.
Similarly, an old one is equivalent to 1/3 new ones, that is, the old one is equivalent to 1 and 1/3 new ones at work.
In other words, a new job needs 12X(4/3), which is equal to 16 minutes.
Set two machines to work together as 1, then
The new work efficiency is 0. 75
The old work efficiency was 0. 25
The total amount of the first table remains the same.
Efficiency x time = total amount
New copier 0. 75 16 12
Old copier 0. 25 48 12
The second table time remains the same.
Efficiency x time = total amount
New copier 0. 75 12 8
Old copier 0. 25 12 4
Two machines working at the same time 1 12 12