How do you tell if a fish is a molly or platy?

I have about 3 kinds of mollies and 3 kind of platies in my tank. I have these gold colored ones but I can't tell if they are mollies or platies. The reason why I want to know this is because I am planning to breed them and I want to avoid cross-breedings.

 

It looks like a molly to me. I did a bit of research about orange platy's and molly's and the backfin does not look like a platy to me.

 

What is a back fin?

 

As in he fin at the back of the fish

 

So the only major difference is the backfin?

 

Hard to tell from these pics. . . but looks like a platy to me. Could you try to get a picture of them flaring their fins and attach as a thumbnail?

 

Okay I will try

 

Platies & mollies cannot cross-breed. Platies/swordtails, mollies/guppies those pairs can though.

 

Molly! Looks like a gold panda Molly.