First find Acceleration
[tex]\boxed{\sf Acceleration=\dfrac{v-u}{t}}[/tex]
[tex]\\ \sf\longmapsto Acceleration=\dfrac{42-0}{2}[/tex]
[tex]\\ \sf\longmapsto Acceleration=\dfrac{42}{2}[/tex]
[tex]\\ \sf\longmapsto Acceleration=21m/s^2[/tex]
Using second equation of kinematics
[tex]\boxed{\sf s=ut+\dfrac{1}{2}at^2}[/tex]
[tex]\\ \sf\longmapsto s=0(2)+\dfrac{1}{2}(21)(2)^2[/tex]
[tex]\\ \sf\longmapsto s=21(2)[/tex]
[tex]\\ \sf\longmapsto s=42m[/tex]