On an ideal transformer, the ratio between the number of turns in the primary and the secondary is the same as the ratio between the input and output voltage:
![\frac{N_{\text{ in}}}{N_{\text{out}}}=\frac{V_{\text{ in}}}{V_{\text{out}}}](https://img.qammunity.org/2023/formulas/physics/college/35u0njr631u8ismpt5mpvx52ohe0hqiu0w.png)
Since the secondary has 10 times more turns than the primary, then the output voltage must be 10 times greater than the input voltage.
Therefore, the answer is:
![120V](https://img.qammunity.org/2023/formulas/physics/college/cuu3xf7n9ofge36l4rv7hh9piqy2pghftm.png)