A farmer uses four out of five equal strips of his land for wheat crop and $\dfrac{1}{7}$ of his land for cereal crop. What fraction of his land is available for other crops?

Fraction of land used for wheat crop = $\dfrac{4}{5}$.

Fraction of land used for cereal crop = $\dfrac{1}{7}$.

Total fraction used = $\dfrac{4}{5} + \dfrac{1}{7}$

LCM of 5 and 7 = 35.

$\Rightarrow \dfrac{4 \times 7}{5 \times 7} + \dfrac{1 \times 5}{7 \times 5}\\[1em] \Rightarrow \dfrac{28}{35} + \dfrac{5}{35}\\[1em] \Rightarrow \dfrac{28 + 5}{35}\\[1em] \Rightarrow \dfrac{33}{35}$

Fraction of land available for other crops = $1 - \dfrac{33}{35}$

$\Rightarrow \dfrac{35}{35} - \dfrac{33}{35}\\[1em] \Rightarrow \dfrac{35 - 33}{35}\\[1em] \Rightarrow \dfrac{2}{35}$

Hence, the fraction of land available for other crops = $\dfrac{2}{35}$.