Convert mixed fraction into improper fraction,
$$=3\dfrac{1}{5}=\dfrac{16}{5}$$
$$=\dfrac{16}{5}-\dfrac{7}{10}$$
For subtraction of two unlike fractions,first change them to the like fractions.
LCM of $$5,10 =10$$
Now, let us change each of the given fraction into an equivalent fraction having $$10$$ as the denominator.
$$=\dfrac{16}{5}\times \dfrac{2}{2}=\dfrac{32}{10}$$
$$=\dfrac{7}{10}\times \dfrac{1}{1}=\dfrac{7}{10}$$
Then,
$$=\dfrac{32}{10}-\dfrac{7}{10}$$
$$\dfrac{32-7}{10}$$
$$\dfrac{32-7}{10}$$ $$[divide\ by\ 5]$$
$$=\dfrac{5}{2}$$
$$=2\dfrac{1}{2}$$