[tex]\measuredangle BCE=30[/tex]
Explanation
Step 1
the sum of the internal angles in a triangle equals 180, then
for triangle CDE
[tex]\begin{gathered} rigth\text{ angle+blue angle+yellow angle=180} \\ \text{replace } \\ 90+10+\measuredangle\text{EDC}=180 \\ 100+\measuredangle\text{EDC}=180 \\ \text{subtract 100 }in\text{ both sides} \\ 100+\measuredangle\text{EDC-100}=180-100 \\ \measuredangle\text{EDC}=80 \end{gathered}[/tex]
Step 2
as we can see, in poitn c, we have a 180 degrees angle(ACD)
so
[tex]\begin{gathered} \text{red angle+gre}enangle+yellow\text{ angle}=180 \\ \text{replace} \\ 70+\measuredangle BCE+\measuredangle EDC=180 \\ 70+\measuredangle BCE+80=180 \\ 150+\measuredangle BCE=180 \\ \text{subtract 150 in both sides} \\ 150+\measuredangle BCE-150=180-150 \\ \measuredangle BCE=30 \end{gathered}[/tex]
I hope this helps you
