Answer:
25 students
Explanation:
Let x represent the amount of students in the astronomy club then:
80%x=20
Convert 80% to a fraction. Any percentage is that number over 100:
![(80)/(100)x=20](https://img.qammunity.org/2023/formulas/mathematics/high-school/1mjv4pssxg1iigmya2afx8d01l1r1ch5lp.png)
Simplify the fraction:
![(8)/(10)x=20](https://img.qammunity.org/2023/formulas/mathematics/high-school/8d80z6aiqf5aor8oxmzu6ome9c4w823t1i.png)
![(4)/(5)x=20](https://img.qammunity.org/2023/formulas/mathematics/high-school/fttnvnbdbgpphfo1ykloxi4mamqjb32uvq.png)
Multiply both sides by 5:
![4x=100](https://img.qammunity.org/2023/formulas/mathematics/high-school/ccirdkj7a9q7mtkvjf9c1aim6w8psuc7q3.png)
Divide both sides by 4:
![x=25](https://img.qammunity.org/2023/formulas/mathematics/high-school/h9hnjzi1jy90b3zvdv8htd7on39zh4b0n5.png)
There are 25 students in the astronomy club.