初1幾何 唔識><” sos/.\

Construct two parallel lines, HCK and MDN, which are parallel to AB.
Angle ABC = 25 (given)
Angle BCK = angle ABC = 25 (alt. angles, AB // HK)
Angle BCD = 45 (given)
Angle KCD = angle BCD - angle BCK = 45 - 25 = 20
Angle CDM = angle KCD = 20 (alt. angles, HK // MN)
Angle CDE = 30 (given)
Angle MDE = angle CDE - angle CDM = 30 - 20 = 10
Angle DEF = 10 (given)
that is, Angle MDE = angle DEF = 10
Therefore, MN // EF (alt. angles eq.)
As AB // HK // MN (by construction)
and MN // EF,
AB // HK // MN // EF
AB // EF