we know that
[tex](5k-3)\°+(9+k)\°=180\°[/tex] -------> by supplementary angles
Solve for k
Combine like terms in the left side
[tex]6k+6=180[/tex]
Substract [tex]6[/tex] both sides
[tex]6k=180-6[/tex]
Divide by [tex]6[/tex] both sides
[tex]k=174/6=29\°[/tex]
therefore
the answer is the option
[tex]k=29\°[/tex]
