12.Sum of angle measures: 360°
10a
7a
12a
7a
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Answer:
[tex]given \: that \: sum \: of \: angle = 360 \\ 12a + 7a + 10a + 7a = 360 \\ 36a = 360 \\ a = \frac{360}{36} = 10 \\ a = 10 \\ thank \: you[/tex]