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Answer:
x=16
Step-by-step explanation:
red line^2 = (8 x sq rt 3)^2 - 12^2
red line ^2=191.99-44
red line^2=47.99
red line=6.93
12/6.93=6.93/(x-12) by the geometric mean altitude theorem
12(x-12)=(6.93)(6.93)
x-12=4
x=16