Add the following fractions using the formula $\dfrac{a}{b}+\dfrac{c}{d}=\frac{\boxed{ad}+\boxed{bc}}{\boxed{bd}}=\frac{\boxed{ad+bc}}{\boxed{bd}}$.

An example of a correct calculation would be $\dfrac{1}{2}+\dfrac{-3}{4}=\frac{\boxed{4}+\boxed{-6}}{\boxed{8}}=\frac{\boxed{-2}}{\boxed{8}}$.

Note that in the intermediate stage, you have to use the denominator $bd$ to be marked correct, you should not use a smaller common denominator (if one exists). Also note the final fraction should be left as it is and should not be entered in lowest form (if this is different).