∵AB=BC=CD=ED=EF;
∴∠A=∠ACB,∠CBD=∠BDC,∠DCE=∠CED,∠EDF=∠DFE;
∵∠A=20;
∴∠ACB=20,∠ABC=140;∠CBD=∠BDC=40,∠BCD=100;
∠DCE=∠CED=∠EDC=60;∠EDF=∠DFE=80,∠DEF=20;
∵∠DCE=∠CED=∠EDC=60;
∴CE=CD=BC,∠CBE=∠CEB=10;
∴∠FEB=∠DEF+∠CED-∠CEB=20+60-10=70.
∵AB=BC=CD=ED=EF;
∴∠A=∠ACB,∠CBD=∠BDC,∠DCE=∠CED,∠EDF=∠DFE;
∵∠A=20;
∴∠ACB=20,∠ABC=140;∠CBD=∠BDC=40,∠BCD=100;
∠DCE=∠CED=∠EDC=60;∠EDF=∠DFE=80,∠DEF=20;
∵∠DCE=∠CED=∠EDC=60;
∴CE=CD=BC,∠CBE=∠CEB=10;
∴∠FEB=∠DEF+∠CED-∠CEB=20+60-10=70.