a,\(s_{6s}-s_{t6}=14\Rightarrow v_0t+\dfrac{1}{2}at^2-\left(v_0t+\dfrac{1}{2}a\left(t-1\right)^2\right)=14\)
\(3\cdot6+\dfrac{1}{2}a\cdot6^2-\left(3\cdot6+\dfrac{1}{2}\cdot a\cdot\left(6-1\right)^2\right)=14\Rightarrow a=\dfrac{28}{11}\left(\dfrac{m}{s^2}\right)\)
b,\(s=v_0t+\dfrac{1}{2}at^2=3\cdot5+\dfrac{1}{2}\cdot\dfrac{28}{11}\cdot5^2=\dfrac{515}{11}\left(m\right)\)