How do you simplify (4x^3)/(28x^4)?

(Assuming $x \ne 0$)
$\frac{4 {x}^{3}}{28 {x}^{4}}$
$= \frac{\left(4\right) \left({x}^{3}\right)}{\left(4\right) \left(7\right) \left({x}^{3}\right) \left(x\right)}$
$= \frac{\cancel{\left(4\right)} \cancel{\left({x}^{3}\right)}}{\cancel{\left(4\right)} \left(7\right) \cancel{\left({x}^{3}\right)} \left(x\right)}$
$= \frac{1}{7 x}$