Answer :
[tex]velocity_{final}-velocity_{initial}=\frac{distance}{time}\\\\
v_{initial}=21\frac{m}{s}\\
v_{final}=0\frac{m}{s}\\
time=21s\\\\
\Delta v *time=distance\\\\
distance=|(0-21)*21|=441m
\\\\Bus\ traveled\ 441meters.[/tex]