Create your fractions you want to subtract. You will get a message if your fractions are not proper, if your common denominator is greater than 32, or if your difference would be negative. (You may or may not start with common denominators using fraction circles.)
If you need common denominators, click "Equivalent Fractions." Drag the slider until you find a common denominator that will create equivalent fractions.
Drag the blue point on the right circle to the center of the left circle to see what subtracting will visually remove from the subtrahend.
Click "Subtract Fractions" to actually subtract the two fraction circles.
Write in your solution to see if you found the correct difference!