Setup

a : = $\func$rand(- 5, - 1)

b : = $\func$rand(1, 9)

c : = $\func$rand(10, 30)

Condition: ${\frac{{c-b}}{{a}}}$ = $\left\lfloor\vphantom{ \frac{c-b}{a}}\right.$${\frac{{c-b}}{{a}}}$$\left.\vphantom{ \frac{c-b}{a}}\right\rfloor$