We know that there is 180 degrees in a triangle. Also, we know that a line has a total of 180 degrees across it. With this, we can find Angle C.
First, let's find Angle ACB
70 + 30 + x = 180 (because 180 in a triangle)
100 + x = 180
X = 80
Now that we know angle ACB, we can use that to find Angle BCE.
80 + Y (Angle BCE) = 180 (because 180 along a line)
Y = 100
So Angle BCE is 100 degrees.
I hope this Helps!
