triangle abc is similar to triangle def. write the equation, in slope intercept form, of the side of triangle def that is parallel to bc

Don't know how to find x given these segment lengths

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?

Yvaries inversely as x. y =12 when x=5. find y when x=4