Let e be the number of extra hours that Carla works, then we can set the following equation:
![12\cdot35+18t=492.](https://img.qammunity.org/2023/formulas/mathematics/college/3fr09pha5lxkgoxewcf1zcfml59ourzie8.png)
Simplifying the above equation we get:
![420+18t=492.](https://img.qammunity.org/2023/formulas/mathematics/college/cjfkbwqy0637iafaedqhieg5a823iqw2fn.png)
Subtracting 420 from the above equation we get:
![\begin{gathered} 420+18t-420=492-420, \\ 18t=72. \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/n51a4m7m2pq8ehbxatjkzofgkwqa2r97ms.png)
Dividing the last equation by 18 we get:
![\begin{gathered} (18t)/(18)=(72)/(18), \\ t=4. \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/ryaegasi5tvhun0ejuj1pvhuqsw7gw8p1b.png)
Therefore she worked for 35+4=39 hours.
Answer: 39 hours.