Respuesta :

mhanifa

Answer:

  • m∠ABC = 15°

Step-by-step explanation:

Given

  • m∠ABC = x°
  • m∠BCD = 25°
  • m∠CDE = 55°
  • m∠DEF = 3x°

Add two more parallel lines passing through points C and D.

Consider alternate interior angles formed by the four parallel lines.

The angles between the two middle lines are equal to:

  • m∠BCD - m∠ABC  = m∠CDE - m∠DEF

Substitute values and solve for x:

  • 25 - x = 55 - 3x
  • 3x - x = 55 - 25
  • 2x = 30
  • x = 15

m∠ABC = 15°

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