In triangles AOQ and BOP, we have
$$\angle OAQ=\angle OBP$$ [Each equal to $$90^\circ$$]
$$\angle AOQ=\angle BOP$$ [Vertically opposite angles]
Therefore, by AA-criterion of similarity
$$\triangle AOQ\sim \triangle BOP$$
$$\Rightarrow $$ $$\dfrac { AO }{ BO } =\dfrac { OQ }{ OP } =\dfrac { AQ }{ BP } $$
$$\Rightarrow $$ $$\dfrac { AO }{ BO } =\dfrac { AQ }{ BP } $$
$$\Rightarrow $$ $$\dfrac { 10 }{ 6 } =\dfrac { AQ }{ 9 } $$
$$\Rightarrow $$ $$AQ=\dfrac { 10\times 9 }{ 6 } =15 cm$$