Can someone explain this to me on how you get this cause I’m really confused?

Explanation:
Convert each fraction into an improper function.
In order to do that, take the whole number and multiply it by the denominator.
Then, add the numerator to the product and put it over the denominator.
2[tex]\frac{3}{7}[/tex]: ((2*7 = 14) + 3)/7 = [tex]\frac{17}{7}[/tex]
1[tex]\frac{4}{7}[/tex]: ((1*7 = 7) + 4)/7 = [tex]\frac{11}{7}[/tex]
[tex]\frac{17}{7}[/tex] - [tex]\frac{11}{7}[/tex] = [tex]\frac{6}{7}[/tex]