A number is 5 times bigger than a second number. Both these numbers added together must make 72. What is a system of equations for this?

What is the value of x? enter your answer in the box. photo attached.

Plz heeeeeeelp plz give me the answer

Kayla wants to find the width, ab, of a river. she walks along the edge of the river 65 ft and marks point c. then she walks 25 ft further and marks point d. she turns 90° and walks until her location, point a, and point c are collinear. she marks point e at this location, as shown. (a) can kayla conclude that δ and δ are similar? why or why not? (b) suppose de = 15 ft. what can kayla conclude about the width of the river?