The first step is to figure out what angle DEB is equal to. Check out the attached image. I've marked this as angle y and it is shown in purple.
Note how the purple angle y and the orange 160 degree angle form a straight angle (180 degrees). So the two angles add to 180. Let's solve for y
(orange angle) + (purple angle) = straight angle
(angle CEB) + (angle DEB) = angle CED
y+160 = 180
y+160-160 = 180-160 ... subtract 160 from both sides
y = 20
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Now we can use this to figure out angle x. The three angles x, 115, and 20, combine to 180 degrees as they all glue together to form a straight angle. Let's solve for x:
x+115+y = 180
x+115+20 = 180 ...replace y with 20
x+135 = 180 ......... combine like terms
x+135-135 = 180-135 ...... subtract 135 from both sides
x = 45
Therefore, the final answer is 45
