Time to compute. The working habit that earns full marks, here and in every science course after this one: set up before you solve. Write $v = \dfrac{d}{t}$, put each given number into its own socket — the distance in $d$'s spot, the time in $t$'s — and only then do the arithmetic. It feels slow for about a week; then it feels like a superpower.

And the units ride along for free: metres over seconds comes out in $\mathrm{m/s}$, which is exactly what a speed should wear. If your answer ever comes out dressed wrong, a number went into the wrong socket — the units just told on it.