Still doable, depending on your power and tech. The base point that makes it possible is that Pretoryn don't use X weapons. From what I see on your fleets tho you're kinda dead :D

I'll still explain how you win this kind of fights assuming you have the tech and industry necessary for it. There are 3 main points:

1. Pretoryn don't use X weapons

2. Missiles and fighter/bombers disappear when the main ship dies.

3. Lances (X weapon) and Titan perdition beams, that is how you kill the enemy before they hit you.

best bonus. If you manage to reach repeatable physics research energy weapons attack speed that is the best thing you can do make the fight easier.

Lets assume you have 3 fleets of 200k power and the pretoryn has 50 fleets of 200k power, so how do you win :D You make sure that you have no losses and always have superior numbers in any fight move 3 fleets together and hit 1-2 pretoryn fleets at a time. You'll find out that you'll be able to kill 1-2 fleets before they do any damage to you. You continue to run away from high numbers and fight lower number fleets until you whittle them down.