D = vt + 1/2at^2 D - vt = 1/2at^2 2(D - vt)/t^2 = a

[latex]D=vt+\frac{1}{2}at^2\\\\\frac{1}{2}at^2+vt=D\ \ \ \ /-vt\\\\\frac{1}{2}at^2=D-vt\ \ \ \ /\cdot2\\\\at^2=2D-2vt\ \ \ \ /:t^2\\\\a=\frac{2D-2vt}{t^2}[/latex]