Lets see.. 3/4.. 2/7.. Lets swap it so now its 3/7 and 2/4. X It.. 7x 3 = 21. We need to take the other number's bottom (3/7) So.. 28.. 21/28 Currently. Do the same with the other number. 8/28. So now 8/28 X 21/28 = 168/28 Expect now its uneven. so we have to divide 168 Divided by 28 = 6. No remainder. so 7.. I think is left. You can discuss this with a adult. If this didnt work.