To do subtraction in fractions, we need to equal the number in the denominator. Due that 5 and 7 don't have any number in common, we need to multiply 5 x 7= 35. Then, we multiply the numerator of the fraction with the number that was multiplied in the denominator. Let's see:
[tex]\begin{gathered} \frac{2}{5}\text{ - }\frac{2}{7}= \\ \frac{2(7)}{35}\text{ - }\frac{2(5)}{35}= \\ \frac{14\text{ -10}}{35}= \\ \frac{10}{35}=\text{ No we can simplify the fraction dividing both numbers by 5. } \\ \\ \frac{2}{7} \\ \\ The\text{ answer is }\frac{2}{7} \end{gathered}[/tex]