A certain substance X decomposes. It is found that 50% of X remains after 100 minutes. How much X remains after 200 minutes if the reaction order with respect to X is

zero order: ?

first order: 25% (I was able to calculate this one)

second order: ?

After calculating I thought zero order was 50% and second order was 12.5%, but I am wrong. Can anyone help answer and explain this to me??