I need help I don’t get it

Plot the points (0,6), (3,15.8), and (9.5,0) using the graphing tool, and find the function

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?

Idon’t understand! use slope intercept form to solve: through: (2,5) slope= undefined