solve for y
A. 8
B.
[tex]3 \sqrt{7} [/tex]
C.
[tex]4 \sqrt{7} [/tex]
D. 12
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Triangle ADC and triangle BCD are similar, therefore the sides are in proportion:
[tex]\dfrac{y}{9}=\dfrac{7}{y}[/tex]
cross multiply
[tex]y^2=9\cdot7\to y=\sqrt{9\cdot7}\\\\y=\sqrt9\cdot\sqrt7\\\\y=3\sqrt7[/tex]
Answer: B. 3√7