Okay, so you know 5 moles of sodium ethanedioate reacts with 2 moles of potassium permanganate. You know how much ethanedioate you used (1.44g in 200cm^3, you used 20cm^3 so 0.144g) so you can work out that there's going to be 2/5 of that many moles of permanganate, which you can also get in grams, and divide these by the volume of permanganate you used.