So keep in mind acceleration is velocity over time, or more specifically, Δvelocity / Δtime. You're given a change in velocity and time. So your equation should look like:
[tex] \frac{(7.5-5.0)m/s}{1.25s} [/tex]
Solve that equation, and remember acceleration will be in [tex] \frac{m}{s^{2}} [/tex]!
