Respuesta :

Step-by-step explanation:

a + b = 90

a + c = 180

a) If a = x, the. we can write

x + b = 90 and x + c = 180

or

b = 90 - x

c = 180 - x

b) c - b = (180 - x) - (90 - x)

= 180 - x - 90 + x

= 90

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