We could determine the acceleration using this formula
[tex]\boxed{a= \dfrac{v_{1}-v_{0}}{t}}[/tex]
Joe accelerated from 35 m/s to 50 m/s in 50 seconds, plug in the numbers
a= [tex]\dfrac{v_{1}-v_{0}}{t}[/tex]
a = [tex]\dfrac{50-35}{50}[/tex]
a = [tex]\dfrac{15}{50}[/tex]
a = 0.3
The acceleration is 0.3 m/s²