Answer:
[tex]\large\boxed{vi=\dfrac{d-at}{t}}[/tex]
Step-by-step explanation:
[tex]d=vit+at\qquad\text{subtract}\ at\ \text{from both sides}\\\\d-at=vit+at-at\\\\d-at=vit\qquad\text{divide obth sides by}\ t\\\\\dfrac{d-at}{t}=\dfrac{vit}{t}\\\\\dfrac{d-at}{t}=vi[/tex]
