Answer:
[tex]y=3\sqrt{7}\ units[/tex]
Step-by-step explanation:
see the attached figure with letters to better understand the problem
we know that
In the right triangle ABD
[tex]tan(<BAD)=y/9[/tex]
In the right triangle BCD
[tex]tan(<CBD)=7/y[/tex]
remember that
m< BAD=m<CBD
therefore
[tex]tan(<BAD)=tan(<CBD)[/tex]
equate the equations
[tex]y/9=7/y[/tex]
[tex]y^{2}=63[/tex]
[tex]y=3\sqrt{7}\ units[/tex]
