Answer: Jane must transfer 90 songs from notebook to mobile.
Step-by-step explanation: Given that there are 210 songs in Jane's notebook, while she has 150 songs in her mobile phone.
We are to find the number of songs she must transfer from the notebook to the mobile phone in order to have twice as many songs in the mobile as in the notebook.
Let, 'x' be the number of songs that Jane must transfer from notebook to mobile.
Then, according to the given information, we have
![2(210-x)=150+x\\\\\Rightarrow 420-2x=150+x\\\\\Rightarrow 2x+x=420-150\\\\\Rightarrow 3x=270\\\\\Rightarrow x=90.](https://img.qammunity.org/2020/formulas/mathematics/high-school/ro3ylzybkdoepvvydmaqvxgqqxdkzf3sbl.png)
Thus, Jane must transfer 90 songs from notebook to mobile.