\(\dfrac{12}{13}-\dfrac{21}{26}=\dfrac{24}{26}-\dfrac{21}{26}=\dfrac{24-21}{26}=\dfrac{3}{26}\)
\(\dfrac{12}{13}-\dfrac{21}{26}=\dfrac{12\times2}{13\times2}-\dfrac{21}{26}=\dfrac{24}{26}-\dfrac{21}{26}=\dfrac{24-21}{26}=\dfrac{3}{26}\)
\(\dfrac{12}{13}\) - \(\dfrac{21}{26}\)
=\(\dfrac{24}{26}\)-\(\dfrac{21}{26}\)
=\(\dfrac{3}{26}\)