Answer:
cp = rs 400
loss = 10%
Then SP = 400 - 10% of 400
= 400 - 40
= 360
Therefore SP = Rs. 360
You got the method and answer correct in this question, congrats!
The second answer.
You have the first prize, x.
Then you have the second prize, which is x - 50.
Then you have the third prize, which is x - 50 -50, or x - 100.
So the total money is:
x + (x-50) + (x-100).