Answer:
A senior citizen costs $8
Explanation:
Represent senior citizens with S and children with C.
The first day is represented as:
![3S + C = 38](https://img.qammunity.org/2021/formulas/mathematics/high-school/qmdghfb21c8etl7zfno1be8vfcmy0htsdy.png)
The second day is represented as:
![3S + 2C = 52](https://img.qammunity.org/2021/formulas/mathematics/high-school/3kjd3axnj1gc56o9vq3oe3ljk8y5b1s5z3.png)
Required
Solve for C and S
Make C the subject in the first equation
![C = 38 - 3S](https://img.qammunity.org/2021/formulas/mathematics/high-school/pwfj4aghwobpycuuk9z76dusg1olqyelii.png)
Substitute 38 - 3S for C in the second equation
![3S + 2(38 - 3S) = 52](https://img.qammunity.org/2021/formulas/mathematics/high-school/iezndrafgsdfzzlkz8olkfxq8u8x0cf0su.png)
![3S + 76 - 6S = 52](https://img.qammunity.org/2021/formulas/mathematics/high-school/qdqw0fxe6i6fqqpje6yzwuzw70v5qlv679.png)
Collect Like Terms
![3S - 6S = 52 - 76](https://img.qammunity.org/2021/formulas/mathematics/high-school/z1rfybphr1i5ov799dburqyv80meqwp0la.png)
![- 3S = -24](https://img.qammunity.org/2021/formulas/mathematics/high-school/66g7jso5cms8i7kjg575scmq94m4ep2290.png)
Divide through by -3
![S = 8](https://img.qammunity.org/2021/formulas/mathematics/high-school/6fbndril3yil0k24kq0z43jgyyyytk5djc.png)
Recall that:
![C = 38 - 3S](https://img.qammunity.org/2021/formulas/mathematics/high-school/pwfj4aghwobpycuuk9z76dusg1olqyelii.png)
![C = 38 - 3 * 8](https://img.qammunity.org/2021/formulas/mathematics/high-school/9dhkzle5nxaii4kke9nsbermevwu6k79w9.png)
![C = 38 - 24](https://img.qammunity.org/2021/formulas/mathematics/high-school/cj5vpdwqbik05no2vnm7mwaq295k0i5cmv.png)
![C = 14](https://img.qammunity.org/2021/formulas/mathematics/high-school/i8pelhibnel7vkn1yzlrnmineoqxyj38jl.png)
Hence, a senior citizen costs $8