Hello,
This question is very easy. :) If she use phone everyday at 45 minutes, x days => 45x use.
Later x day, She use 540 minutes.
be 45x=540
x,
540/45 = 12
We see in the link:
https://brainly.com/question/16038184?answeringSource=feedPersonal%2FhomePage%2F7
Good lessons!