Evaluate:
$$\cfrac{3}{4}$$ $$-\left(\cfrac{4}{5}\right)$$
$$\cfrac{3}{4}$$ $$-\left(\cfrac{4}{5}\right)$$
To subtract rational numbers their denominator should be same, so we can simply subtract their numerator and denominator will remain common.
$$LCM$$ of $$4$$ and $$5$$ is $$20$$
Let's express each of the given rational numbers with the above $$LCM$$ as the common denominator.
Now,
$$\cfrac{3}{4}=\cfrac{(3\times (5))}{(4\times(5))}=\cfrac{15}{20}$$
$$\cfrac{4}{5}=\cfrac{(4\times (4))}{(5\times(4))}=\cfrac{16}{20}$$
So,
$$\cfrac{3}{4}$$ $$-\left(\cfrac{4}{5}\right)=\cfrac{15}{20}-\left(\cfrac{16}{20}\right)$$
$$=\cfrac{15-16}{20}$$
$$=\cfrac{-1}{20}$$