In this question , it is given that, you increase your walking speed from 6 m/s to 12 m/s in a period of 2 s.
And the formula of acceleration is the ratio of change in velocity and change in time, that is
![acceleration, a = (v_(2) - v_(1))/(t_(2) - t_(1))](https://img.qammunity.org/2019/formulas/mathematics/high-school/88otm8ck3h3658ktv4riuqyohhv17mxzl9.png)
Substituting the values in the formula, we will get
![a = (12-6)/(2-0) = (6)/(2) = 3m/s^2](https://img.qammunity.org/2019/formulas/mathematics/high-school/ejfcycd0ze7dq1x2zzbpudluxh1iaz136p.png)