Why do we need to know about unit rates

Can someone me i’m confused. will give brainliest and a whole bunch of points

The first side of a triangle measures 5 in less than the second side, the third side is 3 in more than the first side, and the perimeter is 17 in. how long is the third side? if s represents the length of the second side, which of the following represents the length of the third side? s-5 ws-2 s+ 3 next question ask for turn it in

In one month jillian made 36 local phone calls and 20 long-distance calls what was her ratio of local calls to long-distance calls for that month?