I need help with this geometry!

Answer:
[tex]7.8(sin23^o)[/tex]
Step-by-step explanation:
[tex]Sin23=\frac{opp}{hyp}[/tex]
[tex]Sin23=\frac{BC}{7.8}[/tex]
[tex]0.3907=\frac{BC}{7.8}[/tex]
[tex]BC=3.04746[/tex]
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hope it helps...
have a great day!!