kinematics equations, the unknown

Notice the unknown in every equation.

No	Equation	Uknown
(C1)	$v = v_0 + a t$	$x - x_0$
(C2)	$x - x_0 = v_0 t + \tfrac12 a t^2$	$v_t$
(C3)	$v^2 = v_0^2 + 2a(x - x_0)$	$t$
(C4)	$x - x_0 = v t - \tfrac12 a t^2$	$v_0$
(C5)	$x - x_0 = \tfrac12 (v_0 + v) t$	$a$

The term $x - x_0$ is also written as $\Delta x$ or $s$ , and there are other variations, e.g. $x = x_t = x(t)$ , $v = v_t = v(t)$ , etc.