To find the part-to-part ratio of fitness trackers to phones, you can compare the number of students who voted for each device.
According to the data provided:
- Number of fitness trackers: 5
- Number of phones: 7
The part-to-part ratio of fitness trackers to phones is simply 5 to 7, which can be written using a colon as:
5:7
So, the correct answer is 5:7.