we know that
The Intersecting Secant Theorem states that when two secant lines intersect each other outside a circle, the products of their segments are equal
so
in this problem
[tex]TV*UV=SV*RV[/tex]
we have
[tex]TV=a\ units\\UV=12\ units\\SV=4\ units\\RV=9\ units[/tex]
substitute the values and solve for a
[tex]a*12=4*9[/tex]
[tex]a=36/12=3\ units[/tex]
therefore
the answer is
The length of TV is [tex]3\ units[/tex]
