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Respuesta :

Answer:

m∡ZA = 51°

m∡ZB = 39°

Step-by-step explanation:

∡ZB = 'b'

∡ZA = '12 + b'

b + 12 + b = 90

2b + 12 = 90

2b = 78

b = 39

12 + 39 = 51