(NH4)2S2O8 I2 --> gives what ?
(NH4)2S2O8 KI --> gives what ?
please answer me or if u can send me a chemistry website for solving equations.. thanks

The disulfate molecule is an oxidising agent, and Iodine, like iodide are reductants. Can you guess the reaction taking place?

Are you familiar with the reaction? I would find it strange that your teacher gives you those questions without doing examples in class or doing the experiment.