Answer:
answers down below :p
Step-by-step explanation:
12 use a calculator i did it
Given that triangle ABC is right angle triangle. CD is altitude such that AD=BC
ABC is a right angle triangle so apply Pythogorean theorem

(Given that AD = BC)
(Given that AB=3)
...(i)
ADC is a right angle triangle so apply Pythogorean theorem



...(ii)
Plug value (ii) into (i)





Hence final answer is 
Any value as long as P = Q
For the equation to have infinitely many solutions, we require both sides of the equation to have exactly the same terms.