How long does it take for Marks car to change to its velocity from 12 m/s to 25 m/s if the acceleration is 5 m/s ​2

v = u + a*t   where v = final velocity (25m/s), u = initial velocity (12m/s), a = acceleration (5m/s²) and t = time (secs)

So t = (v - u)/a  

I'll leave you to fill in the numbers.

How long does it take for Marks car to change to its velocity from 12 m/s to 25 m/s if the acceleration is 5 m/s2

a = acceleration

v = velocity

t = time

$\begin{array}{rcll} \boxed{~ \begin{array}{rcll} a &=& \frac{ \Delta v } { \Delta t } \end{array} ~}\\\\ \Delta v &=& 25\ \frac{m}{s} - 12\ \frac{m}{s} \\ a &=& 5\ \frac{m}{s^2} \\\\ \end{array}\\\\ \begin{array}{rcll} 5\ \frac{m}{s^2} &=& \frac{ 25\ \frac{m}{s} - 12\ \frac{m}{s} } { \Delta t } \\ 5\ \frac{m}{s^2} &=& \frac{ 13\ \frac{m}{s} } { \Delta t } \\ \Delta t &=& \frac{ 13\ \frac{m}{s} } { 5\ \frac{m}{s^2} } \\ \Delta t &=& \frac{ 13 } { 5 } \ s \\ \mathbf{ \Delta t } &\mathbf{=}& \mathbf{2.6 \ s }\\ \end{array}$