Question

Need answers before 8pm!!

Answer 1

We have similar triangles so

12/x = (12+78)/(x+13)

We can skip some algebra by doing the ratio on the pieces.  We'll show it works at the end.

12/x = 78/13

x = 12(13)/78 = 2

We check

12/2 = 6

(12+78)/(2+13) = 90/15 = 6, good

Answer: x=2