As they were giving away free pens to each of the first 200 people who come into the store, it means they had a total number of 200 pens.
In the first hour they gave away 75% of the pens, then we need to calculate the 75% of 200:
![200*\frac{75\text{ \%}}{100\text{ \%}}=200*0.75=150](https://img.qammunity.org/2023/formulas/mathematics/college/4n3rdv3ad9s56der1ia8qiu9rghqzh217x.png)
Then, in the first hour, they gave away 150 pens.