Idon't understand how u came to that conclusion

One side of a rectangle is 7 feet shorter than seven times the other side. find the length of the shorter side if we also know that the perimeter of the rectangle is 306 feet.

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

Can someone explain to me how to do