First you need to change 6 2/5 to an improper fraction and 4 3/7 to an i promover fraction. Then find equivalent fractions for both but keep in mind that you need to have the same denominator. Finally subtract and you have you answer
6 2/5 = 32/5
4 3/7 = 31/7
32/5 • 7 (multiply by numerator and denominator by 7)
31/7 • 5 (multiply by numerator and denominator by 5)
224/35 - 217/35 = X
X = 7/35
7/35 divided by 7 = 1/5
