Question

помогите пожалуйста!

Answer 1

$( frac{13}{14}-x )-a= frac{15}{21} \ \ x= frac{1}{7} \ \ ( frac{13}{14}-frac{1}{7} )-a= frac{15}{21} \ \ frac{11}{14}-a= frac{15}{21} \ \ a= frac{11}{14}- frac{15}{21} \ \ a= frac{1}{14}$