20 are Macs, and 4 are PC
Step by Step:
We have a ratio here, 2 PC for every 10 Mac, so the ratio can be written as 2:10
Which is simply comparing the number of pc(2) to the number of macs(10), next with the ratio 2:10 we take the total amount of devices which is 12 in this ratio( 2 PC and 10 Macs) then u write it as 2/12:10/12.. so in 12 computers 2 are pc and 10 are mac.. in the next case we have 24 computers so it’s the double of 12 so double macs and double pc.. So 20 Mac and 4 PC