Question

1) Determine n utilizando a propriedade comutativa.
a) 235+n= 100+25
b) n + 200= 200+300
c) (n+2) + 250 = 250 + 10
d) (n-3) + (-25) + 40
e) (-120) +(3-n)= (n+1) + (-120)

Answer 1

a)
235+n= 100+25
235 + n = 125
n = 125 - 235
n = - 110
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b)
n + 200= 200+300
n + 200 = 500
n = 500 - 200
n = 300
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c)
(n+2) + 250 = 250 + 10 
n + 2 = 250 - 250 + 10
n + 2 = 0 + 10
n = 10 - 2
n = 8
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d) sinal de "=":

(n-3) = (-25) + 40
n - 3 = - 25 + 40
n - 3 = 15
n = 15 + 3
n = 18

d)
(n-3) + (-25) = 40
n - 3 - 25 = 40
n - 28 = 40
n = 40 + 28
n = 68
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e)
(-120) +(3-n)= (n+1) + (-120)
- 120 + 3 - n = n + 1 - 120
- 117 - n = n - 119
- 117 + 119 = n + n
2 = 2n
2n = 2
n = 2/2
n = 1