If you can, please show step by step explanation. —7th grader

Answer:
180-x = DCE
Step-by-step explanation:
BCE = 180 degrees since it is a straight line
BCE = BCD + DCE since these are the two angles that make the line
180 = BCD + DCE
We know BCD = x
180 = x + DCE
Subtract x from each side
180-x = DCE