图不准,见谅
∵EM∥CD
∴△AEM∽△ACD,∠AEM=∠ACD
∴AE:AC=AM:AD=3:(3+5)=3:8
又∵AN:AB=3:8
∴△ANE∽△ABC
∴∠ACB=∠AEN
∴∠DCB
=∠ACB+∠ACD
=∠AEN+∠AEM
=∠NEM=70°
图不准,见谅
∵EM∥CD
∴△AEM∽△ACD,∠AEM=∠ACD
∴AE:AC=AM:AD=3:(3+5)=3:8
又∵AN:AB=3:8
∴△ANE∽△ABC
∴∠ACB=∠AEN
∴∠DCB
=∠ACB+∠ACD
=∠AEN+∠AEM
=∠NEM=70°