Respuesta :

mhanifa

Answer:

  • 69°

Step-by-step explanation:

Complementary angles sum to 90°.

We have the measure of one angle, find the missing one as below.

  • m∠A + m∠B = 90°
  • 21° + m∠B = 90°
  • m∠B = 90° - 21°
  • m∠B = 69°
  • <B be x

Complementary angles have sum 90°

[tex]\\ \sf\longmapsto x+21=90[/tex]

[tex]\\ \sf\longmapsto x=90-21[/tex]

[tex]\\ \sf\longmapsto x=69[/tex]