We have the following:
To find the percent markup, we must calculate the profits, knowing that there are 300 shirts and they sell them for a total of $ 20
![300\cdot20=6000](https://img.qammunity.org/2023/formulas/mathematics/college/kwyte23zu128lt4ibuhaxlw1so4if4ovjz.png)
Now we subtract from what was initially spent and then divide by that same amount and multiplying by 100 we will know the percent markup
![(6000-3600)/(3600)\cdot100=66.67\cong67](https://img.qammunity.org/2023/formulas/mathematics/college/yt0k0hh3pjcb1p43f58lhefbatssalaukv.png)
Which means that the percent markup is 67%