Fractions: Adding and Subtracting

Notice that the denominators are different.

We need to multiply both fractions to make their denominators 14. This means multiplying $\dfrac{1}{2}$ by $\dfrac{7}{7}$, and $\dfrac{2}{7}$ by $\dfrac{2}{2}$.

$\dfrac{1}{2} \times \dfrac{7}{7} = \dfrac{7}{14}$ and $\dfrac{2}{7} \times \dfrac{2}{2}=\dfrac{4}{14}$

$\dfrac{7}{14}-\dfrac{4}{14}=\dfrac{3}{14}$

The answer is $\dfrac{3}{14}$