Let,
Number of Advance Tickets = a
Number of Same-Day tickets = s
Given,
Total 45 tickets sold
We can write
![a+s=45](https://img.qammunity.org/2023/formulas/mathematics/high-school/sj8y60r7h4j6jyun601r4pd0nizt6ihahq.png)
Also, each advance ticket cost $15 and same day tickets cost $20 for a total of $825. Thus, we can write:
![15a+20s=825](https://img.qammunity.org/2023/formulas/mathematics/high-school/mupdf1m8gzwph30uy18r488csoo3ew3j6o.png)
We will multiply the first equation by - 15 and then add both equations. Then, solve for "s". The steps are shown below:
![\begin{gathered} -15*\lbrack a+s=45\rbrack \\ -15a-15s=-675 \\ ------------- \\ -15a-15s=-675 \\ 15a+20s=825 \\ ------------- \\ 5s=150 \\ s=(150)/(5) \\ s=30 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/high-school/p2ybemh0wnzslrg0g1n5i0duo6w7zdqn1y.png)
Now, we can use this value of "s" and put it into Equation 1 and find the value of "a". Shown below:
![\begin{gathered} a+s=45 \\ a+30=45 \\ a=45-30 \\ a=15 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/high-school/i69sap3sefx70nepcz35wr68z0vqedei3s.png)
Answer
Number of advance tickets sold: 15
Number of same-day tickets sold: 30