Question

three lines AB CD EF intersects with each other at O. If AOE=30°AND DOB=40°find COF

Answer 1

$angle \: aeo + eob + dob = 180 \\ 30 + dob + 40 = 180 \\ dob = 180 - 70 = 110 \\ dob = 110 \\ dob = cof \: (alternate \: angles) \\ cof = 110$