Ravi ,
I'm sorry to inform you but only your 12th result is acceptable and it needs to be more than 75% or in case of state board your marks should be within 20 percentile of the total rank. You can check your state board 20 percentile from JOSAA website. But, your 10th result is never counted for getting a seat in IIT.
Now, you only got 50% in 12th that means you are not eligible to join any IIT. You can join any other state engineering colleges or else you can repeat your 12th to increase your percentage beyond 75 percent.


Hope this helps!