What is the solution of y=2x+6 and -2x+y=6

Can someone answer these problems for me

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?

Which shows the first equation written in slope-intercept form? 1/2 (2y + 10) = 7x