Answer:
[tex]25x + 57 + x = 45x(sum \: of \: two \: opposite \:interior \: angles \: is \: equal \: to \: exterior \: ange)\\ 26x + 57 = 45x \\ 57 = 45x - 26x \\ 57 = 19x \\ \frac{57}{19} = x \\ x = 3[/tex]
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