Answer:
[tex]b =5 1 \: \: \: degrees \\ [/tex]
Step-by-step explanation:
Angles in a straight line =180 degrees
[tex]90 + 39 + b = 180 \\12 9 + b = 180 \\ b = 180 - 129 \\ b =5 1 \: \: \: degrees[/tex]
hope this helps
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