the general equation for velocity in terms of acceleration and displacement is: v² = v₀² + 2ax.
Solve for a: a = (v² - v₀²)/(2x).
You are given v₀ and v, and x is easy to calculate since you are given its initial and final values. The rest is just arithmetic.
(note also: SI expressions have a required space between the coefficient and the unit symbol. Thus you should have things such as “15 m” and “-2 m·sˉ¹” instead of “15m” and “-2m·sˉ¹”.)
